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 $141.72   7.606%   $152.4992   $152.50   $152.50   $152.50  
  Purchase #2 $63.69   4.727%   $66.7006   $66.70   $66.70   $66.70  
  Purchase #3 $216.45   12.207%   $242.8721   $242.87   $242.85   $242.90  
  Purchase #4 $55.87   9.630%   $61.2503   $61.25   $61.25   $61.30  
  Purchase #5 $221.91   10.826%   $245.934   $245.93   $245.95   $245.90  
  Purchase #6 $194.33   10.637%   $215.0009   $215.00   $215.00   $215.00  
  Purchase #7 $194.88   4.203%   $203.0708   $203.07   $203.05   $203.10  
  7 purchase totals = $1,088.85       $1,187.3279   $1,187.32   $1,187.30   $1,187.40