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 $82.54   13.576%   $93.7456   $93.75   $93.75   $93.70  
  Purchase #2 $87.49   8.841%   $95.225   $95.23   $95.25   $95.20  
  Purchase #3 $101.82   12.220%   $114.2624   $114.26   $114.25   $114.30  
  Purchase #4 $180.30   13.467%   $204.581   $204.58   $204.60   $204.60  
  Purchase #5 $151.54   10.324%   $167.185   $167.19   $167.20   $167.20  
  Purchase #6 $209.51   9.323%   $229.0426   $229.04   $229.05   $229.00  
  Purchase #7 $68.86   13.110%   $77.8875   $77.89   $77.90   $77.90  
  7 purchase totals = $882.06       $981.9291   $981.94   $982.00   $981.90