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 $87.44   7.712%   $94.1834   $94.18   $94.20   $94.20  
  Purchase #2 $96.26   11.230%   $107.07   $107.07   $107.05   $107.10  
  Purchase #3 $103.86   9.319%   $113.5387   $113.54   $113.55   $113.50  
  Purchase #4 $133.80   5.218%   $140.7817   $140.78   $140.80   $140.80  
  Purchase #5 $62.94   4.781%   $65.9492   $65.95   $65.95   $65.90  
  Purchase #6 $158.84   7.265%   $170.3797   $170.38   $170.40   $170.40  
  Purchase #7 $72.40   11.317%   $80.5935   $80.59   $80.60   $80.60  
  7 purchase totals = $715.54       $772.4962   $772.49   $772.55   $772.50