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 $112.40   5.845%   $118.9698   $118.97   $118.95   $119.00  
  Purchase #2 $164.89   13.306%   $186.8303   $186.83   $186.85   $186.80  
  Purchase #3 $143.81   12.610%   $161.9444   $161.94   $161.95   $161.90  
  Purchase #4 $43.95   10.500%   $48.5648   $48.56   $48.55   $48.60  
  Purchase #5 $129.96   13.481%   $147.4799   $147.48   $147.50   $147.50  
  Purchase #6 $59.53   6.376%   $63.3256   $63.33   $63.35   $63.30  
  Purchase #7 $26.68   5.741%   $28.2117   $28.21   $28.20   $28.20  
  7 purchase totals = $681.22       $755.3265   $755.32   $755.35   $755.30