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 $104.79   8.768%   $113.978   $113.98   $114.00   $114.00  
  Purchase #2 $83.97   8.395%   $91.0193   $91.02   $91.00   $91.00  
  Purchase #3 $91.73   7.202%   $98.3364   $98.34   $98.35   $98.30  
  Purchase #4 $25.51   12.383%   $28.6689   $28.67   $28.65   $28.70  
  Purchase #5 $132.62   6.251%   $140.9101   $140.91   $140.90   $140.90  
  Purchase #6 $170.66   8.357%   $184.9221   $184.92   $184.90   $184.90  
  Purchase #7 $144.46   8.210%   $156.3202   $156.32   $156.30   $156.30  
  7 purchase totals = $753.74       $814.1550   $814.16   $814.10   $814.10