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 $146.26   11.381%   $162.9059   $162.91   $162.90   $162.90  
  Purchase #2 $239.93   8.830%   $261.1158   $261.12   $261.10   $261.10  
  Purchase #3 $74.73   7.749%   $80.5208   $80.52   $80.50   $80.50  
  Purchase #4 $229.66   3.828%   $238.4514   $238.45   $238.45   $238.50  
  Purchase #5 $57.38   13.298%   $65.0104   $65.01   $65.00   $65.00  
  Purchase #6 $175.61   12.676%   $197.8703   $197.87   $197.85   $197.90  
  Purchase #7 $54.54   3.313%   $56.3469   $56.35   $56.35   $56.30  
  7 purchase totals = $978.11       $1,062.2215   $1,062.23   $1,062.15   $1,062.20