Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $151.94   10.716%   $168.2219   $168.22   $168.20   $168.20  
  Purchase #2 $121.78   9.366%   $133.1859   $133.19   $133.20   $133.20  
  Purchase #3 $232.66   11.814%   $260.1465   $260.15   $260.15   $260.10  
  Purchase #4 $112.84   4.768%   $118.2202   $118.22   $118.20   $118.20  
  Purchase #5 $241.90   10.581%   $267.4954   $267.50   $267.50   $267.50  
  Purchase #6 $160.75   10.592%   $177.7766   $177.78   $177.80   $177.80  
  Purchase #7 $183.92   7.760%   $198.1922   $198.19   $198.20   $198.20  
  7 purchase totals = $1,205.79       $1,323.2387   $1,323.25   $1,323.25   $1,323.20