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 $102.60   9.222%   $112.0618   $112.06   $112.05   $112.10  
  Purchase #2 $175.63   11.137%   $195.1899   $195.19   $195.20   $195.20  
  Purchase #3 $169.45   4.824%   $177.6243   $177.62   $177.60   $177.60  
  Purchase #4 $62.90   4.446%   $65.6965   $65.70   $65.70   $65.70  
  Purchase #5 $245.34   10.625%   $271.4074   $271.41   $271.40   $271.40  
  Purchase #6 $92.36   11.130%   $102.6397   $102.64   $102.65   $102.60  
  Purchase #7 $246.96   9.302%   $269.9322   $269.93   $269.95   $269.90  
  7 purchase totals = $1,095.24       $1,194.5518   $1,194.55   $1,194.55   $1,194.50