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 $174.76   11.584%   $195.0042   $195.00   $195.00   $195.00  
  Purchase #2 $232.90   10.123%   $256.4765   $256.48   $256.50   $256.50  
  Purchase #3 $67.26   7.627%   $72.3899   $72.39   $72.40   $72.40  
  Purchase #4 $233.52   11.745%   $260.9469   $260.95   $260.95   $260.90  
  Purchase #5 $207.86   6.810%   $222.0153   $222.02   $222.00   $222.00  
  Purchase #6 $32.99   12.471%   $37.1042   $37.10   $37.10   $37.10  
  Purchase #7 $250.47   7.481%   $269.2077   $269.21   $269.20   $269.20  
  7 purchase totals = $1,199.76       $1,313.1447   $1,313.15   $1,313.15   $1,313.10