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 $207.47   7.491%   $223.0116   $223.01   $223.00   $223.00  
  Purchase #2 $120.56   3.180%   $124.3938   $124.39   $124.40   $124.40  
  Purchase #3 $49.56   6.133%   $52.5995   $52.60   $52.60   $52.60  
  Purchase #4 $99.46   5.601%   $105.0308   $105.03   $105.05   $105.00  
  Purchase #5 $44.60   8.282%   $48.2938   $48.29   $48.30   $48.30  
  Purchase #6 $85.95   10.606%   $95.0659   $95.07   $95.05   $95.10  
  Purchase #7 $53.58   8.428%   $58.0957   $58.10   $58.10   $58.10  
  7 purchase totals = $661.18       $706.4911   $706.49   $706.50   $706.50