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 $88.28   7.863%   $95.2215   $95.22   $95.20   $95.20  
  Purchase #2 $47.33   11.734%   $52.8837   $52.88   $52.90   $52.90  
  Purchase #3 $195.34   10.618%   $216.0812   $216.08   $216.10   $216.10  
  Purchase #4 $90.51   13.513%   $102.7406   $102.74   $102.75   $102.70  
  Purchase #5 $194.36   8.217%   $210.3306   $210.33   $210.35   $210.30  
  Purchase #6 $160.36   5.324%   $168.8976   $168.90   $168.90   $168.90  
  Purchase #7 $56.94   13.122%   $64.4117   $64.41   $64.40   $64.40  
  7 purchase totals = $833.12       $910.5669   $910.56   $910.60   $910.50