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 $182.75   6.156%   $194.0001   $194.00   $194.00   $194.00  
  Purchase #2 $99.58   4.150%   $103.7126   $103.71   $103.70   $103.70  
  Purchase #3 $39.42   8.369%   $42.7191   $42.72   $42.70   $42.70  
  Purchase #4 $153.75   7.838%   $165.8009   $165.80   $165.80   $165.80  
  Purchase #5 $232.33   11.382%   $258.7738   $258.77   $258.75   $258.80  
  Purchase #6 $35.72   11.263%   $39.7431   $39.74   $39.75   $39.70  
  Purchase #7 $232.49   12.703%   $262.0232   $262.02   $262.00   $262.00  
  7 purchase totals = $976.04       $1,066.7728   $1,066.76   $1,066.70   $1,066.70