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 $41.57   11.390%   $46.3048   $46.30   $46.30   $46.30  
  Purchase #2 $194.98   9.733%   $213.9574   $213.96   $213.95   $214.00  
  Purchase #3 $121.79   11.119%   $135.3318   $135.33   $135.35   $135.30  
  Purchase #4 $179.81   11.267%   $200.0692   $200.07   $200.05   $200.10  
  Purchase #5 $209.31   11.683%   $233.7637   $233.76   $233.75   $233.80  
  Purchase #6 $140.52   7.853%   $151.555   $151.56   $151.55   $151.60  
  Purchase #7 $109.27   5.311%   $115.0733   $115.07   $115.05   $115.10  
  7 purchase totals = $997.25       $1,096.0552   $1,096.05   $1,096.00   $1,096.20