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 $65.74   13.686%   $74.7372   $74.74   $74.75   $74.70  
  Purchase #2 $206.45   12.207%   $231.6514   $231.65   $231.65   $231.70  
  Purchase #3 $81.40   13.325%   $92.2466   $92.25   $92.25   $92.20  
  Purchase #4 $231.89   11.340%   $258.1863   $258.19   $258.20   $258.20  
  Purchase #5 $74.74   5.788%   $79.066   $79.07   $79.05   $79.10  
  Purchase #6 $157.74   10.203%   $173.8342   $173.83   $173.85   $173.80  
  Purchase #7 $200.27   7.846%   $215.9832   $215.98   $216.00   $216.00  
  7 purchase totals = $1,018.23       $1,125.7049   $1,125.71   $1,125.75   $1,125.70