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 $66.95   11.592%   $74.7108   $74.71   $74.70   $74.70  
  Purchase #2 $217.73   13.122%   $246.3005   $246.30   $246.30   $246.30  
  Purchase #3 $92.93   13.252%   $105.2451   $105.25   $105.25   $105.20  
  Purchase #4 $219.34   7.429%   $235.6348   $235.63   $235.65   $235.60  
  Purchase #5 $203.75   8.264%   $220.5879   $220.59   $220.60   $220.60  
  Purchase #6 $16.65   11.178%   $18.5111   $18.51   $18.50   $18.50  
  Purchase #7 $199.50   13.770%   $226.9712   $226.97   $226.95   $227.00  
  7 purchase totals = $1,016.85       $1,127.9614   $1,127.96   $1,127.95   $1,127.90