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 $92.57   3.364%   $95.6841   $95.68   $95.70   $95.70  
  Purchase #2 $246.32   3.168%   $254.1234   $254.12   $254.10   $254.10  
  Purchase #3 $51.84   5.381%   $54.6295   $54.63   $54.65   $54.60  
  Purchase #4 $128.45   5.641%   $135.6959   $135.70   $135.70   $135.70  
  Purchase #5 $63.70   10.585%   $70.4426   $70.44   $70.45   $70.40  
  Purchase #6 $156.40   4.214%   $162.9907   $162.99   $163.00   $163.00  
  Purchase #7 $14.64   13.641%   $16.637   $16.64   $16.65   $16.60  
  7 purchase totals = $753.92       $790.2032   $790.20   $790.25   $790.10