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 $94.80   11.551%   $105.7503   $105.75   $105.75   $105.80  
  Purchase #2 $104.76   10.632%   $115.8981   $115.90   $115.90   $115.90  
  Purchase #3 $219.98   12.184%   $246.7824   $246.78   $246.80   $246.80  
  Purchase #4 $155.32   13.637%   $176.501   $176.50   $176.50   $176.50  
  Purchase #5 $233.55   13.675%   $265.488   $265.49   $265.50   $265.50  
  Purchase #6 $231.87   12.254%   $260.2833   $260.28   $260.30   $260.30  
  Purchase #7 $85.69   6.703%   $91.4338   $91.43   $91.45   $91.40  
  7 purchase totals = $1,125.97       $1,262.1369   $1,262.13   $1,262.20   $1,262.20