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 $88.95   4.794%   $93.2143   $93.21   $93.20   $93.20  
  Purchase #2 $229.78   3.121%   $236.9514   $236.95   $236.95   $237.00  
  Purchase #3 $201.28   13.827%   $229.111   $229.11   $229.10   $229.10  
  Purchase #4 $232.96   11.653%   $260.1068   $260.11   $260.10   $260.10  
  Purchase #5 $152.71   6.779%   $163.0622   $163.06   $163.05   $163.10  
  Purchase #6 $133.61   4.159%   $139.1668   $139.17   $139.15   $139.20  
  Purchase #7 $23.70   6.486%   $25.2372   $25.24   $25.25   $25.20  
  7 purchase totals = $1,062.99       $1,146.8497   $1,146.85   $1,146.80   $1,146.90