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 $84.31   13.446%   $95.6463   $95.65   $95.65   $95.60  
  Purchase #2 $149.46   9.368%   $163.4614   $163.46   $163.45   $163.50  
  Purchase #3 $167.87   7.332%   $180.1782   $180.18   $180.20   $180.20  
  Purchase #4 $209.67   12.746%   $236.3945   $236.39   $236.40   $236.40  
  Purchase #5 $66.48   5.254%   $69.9729   $69.97   $69.95   $70.00  
  Purchase #6 $133.87   5.255%   $140.9049   $140.90   $140.90   $140.90  
  Purchase #7 $59.84   12.861%   $67.536   $67.54   $67.55   $67.50  
  7 purchase totals = $871.50       $954.0942   $954.09   $954.10   $954.10