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 $46.66   3.497%   $48.2917   $48.29   $48.30   $48.30  
  Purchase #2 $212.94   11.342%   $237.0917   $237.09   $237.10   $237.10  
  Purchase #3 $87.64   8.486%   $95.0771   $95.08   $95.10   $95.10  
  Purchase #4 $144.56   3.632%   $149.8104   $149.81   $149.80   $149.80  
  Purchase #5 $60.62   7.177%   $64.9707   $64.97   $64.95   $65.00  
  Purchase #6 $167.28   7.718%   $180.1907   $180.19   $180.20   $180.20  
  Purchase #7 $173.91   6.447%   $185.122   $185.12   $185.10   $185.10  
  7 purchase totals = $893.61       $960.5543   $960.55   $960.55   $960.60