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 $162.49   3.122%   $167.5629   $167.56   $167.55   $167.60  
  Purchase #2 $23.95   8.331%   $25.9453   $25.95   $25.95   $25.90  
  Purchase #3 $213.39   10.132%   $235.0107   $235.01   $235.00   $235.00  
  Purchase #4 $240.92   10.791%   $266.9177   $266.92   $266.90   $266.90  
  Purchase #5 $31.87   10.707%   $35.2823   $35.28   $35.30   $35.30  
  Purchase #6 $100.59   3.787%   $104.3993   $104.40   $104.40   $104.40  
  Purchase #7 $99.66   8.495%   $108.1261   $108.13   $108.15   $108.10  
  7 purchase totals = $872.87       $943.2443   $943.25   $943.25   $943.20