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 $68.49   11.475%   $76.3492   $76.35   $76.35   $76.30  
  Purchase #2 $244.31   8.687%   $265.5332   $265.53   $265.55   $265.50  
  Purchase #3 $234.97   3.580%   $243.3819   $243.38   $243.40   $243.40  
  Purchase #4 $28.54   13.569%   $32.4126   $32.41   $32.40   $32.40  
  Purchase #5 $101.26   9.403%   $110.7815   $110.78   $110.80   $110.80  
  Purchase #6 $186.79   4.838%   $195.8269   $195.83   $195.85   $195.80  
  Purchase #7 $139.26   3.206%   $143.7247   $143.72   $143.70   $143.70  
  7 purchase totals = $1,003.62       $1,068.0100   $1,068.00   $1,068.05   $1,067.90