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 $68.50   11.644%   $76.4761   $76.48   $76.50   $76.50  
  Purchase #2 $210.61   7.616%   $226.6501   $226.65   $226.65   $226.70  
  Purchase #3 $149.58   8.289%   $161.9787   $161.98   $162.00   $162.00  
  Purchase #4 $61.98   6.823%   $66.2089   $66.21   $66.20   $66.20  
  Purchase #5 $236.37   10.169%   $260.4065   $260.41   $260.40   $260.40  
  Purchase #6 $190.83   6.165%   $202.5947   $202.59   $202.60   $202.60  
  Purchase #7 $19.39   4.775%   $20.3159   $20.32   $20.30   $20.30  
  7 purchase totals = $937.26       $1,014.6309   $1,014.64   $1,014.65   $1,014.70