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 $33.58   3.785%   $34.851   $34.85   $34.85   $34.90  
  Purchase #2 $142.44   12.851%   $160.745   $160.75   $160.75   $160.70  
  Purchase #3 $32.42   8.808%   $35.2756   $35.28   $35.30   $35.30  
  Purchase #4 $146.43   13.304%   $165.911   $165.91   $165.90   $165.90  
  Purchase #5 $189.96   7.733%   $204.6496   $204.65   $204.65   $204.60  
  Purchase #6 $115.60   11.645%   $129.0616   $129.06   $129.05   $129.10  
  Purchase #7 $23.39   8.478%   $25.373   $25.37   $25.35   $25.40  
  7 purchase totals = $683.82       $755.8668   $755.87   $755.85   $755.90