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 $53.65   11.271%   $59.6969   $59.70   $59.70   $59.70  
  Purchase #2 $155.68   11.224%   $173.1535   $173.15   $173.15   $173.20  
  Purchase #3 $135.49   11.578%   $151.177   $151.18   $151.20   $151.20  
  Purchase #4 $63.96   7.821%   $68.9623   $68.96   $68.95   $69.00  
  Purchase #5 $155.50   8.503%   $168.7222   $168.72   $168.70   $168.70  
  Purchase #6 $158.33   13.562%   $179.8027   $179.80   $179.80   $179.80  
  Purchase #7 $151.98   8.818%   $165.3816   $165.38   $165.40   $165.40  
  7 purchase totals = $874.59       $966.8962   $966.89   $966.90   $967.00