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 $163.89   10.662%   $181.364   $181.36   $181.35   $181.40  
  Purchase #2 $227.87   6.132%   $241.843   $241.84   $241.85   $241.80  
  Purchase #3 $136.61   11.214%   $151.9294   $151.93   $151.95   $151.90  
  Purchase #4 $200.68   3.246%   $207.1941   $207.19   $207.20   $207.20  
  Purchase #5 $43.79   6.351%   $46.5711   $46.57   $46.55   $46.60  
  Purchase #6 $202.43   7.749%   $218.1163   $218.12   $218.10   $218.10  
  Purchase #7 $53.99   8.332%   $58.4884   $58.49   $58.50   $58.50  
  7 purchase totals = $1,029.26       $1,105.5063   $1,105.50   $1,105.50   $1,105.50