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 $59.84   4.605%   $62.5956   $62.60   $62.60   $62.60  
  Purchase #2 $170.76   12.712%   $192.467   $192.47   $192.45   $192.50  
  Purchase #3 $90.90   9.413%   $99.4564   $99.46   $99.45   $99.50  
  Purchase #4 $190.87   6.744%   $203.7423   $203.74   $203.75   $203.70  
  Purchase #5 $200.36   6.784%   $213.9524   $213.95   $213.95   $214.00  
  Purchase #6 $45.67   7.216%   $48.9655   $48.97   $48.95   $49.00  
  Purchase #7 $189.65   9.837%   $208.3059   $208.31   $208.30   $208.30  
  7 purchase totals = $948.05       $1,029.4851   $1,029.50   $1,029.45   $1,029.60