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 $182.57   6.119%   $193.7415   $193.74   $193.75   $193.70  
  Purchase #2 $212.97   4.797%   $223.1862   $223.19   $223.20   $223.20  
  Purchase #3 $8.32   5.700%   $8.7942   $8.79   $8.80   $8.80  
  Purchase #4 $119.82   10.761%   $132.7138   $132.71   $132.70   $132.70  
  Purchase #5 $95.81   12.534%   $107.8188   $107.82   $107.80   $107.80  
  Purchase #6 $51.56   11.714%   $57.5997   $57.60   $57.60   $57.60  
  Purchase #7 $193.87   3.778%   $201.1944   $201.19   $201.20   $201.20  
  7 purchase totals = $864.92       $925.0486   $925.04   $925.05   $925.00