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 $70.93   6.809%   $75.7596   $75.76   $75.75   $75.80  
  Purchase #2 $207.89   13.425%   $235.7992   $235.80   $235.80   $235.80  
  Purchase #3 $213.54   10.164%   $235.2442   $235.24   $235.25   $235.20  
  Purchase #4 $196.61   9.723%   $215.7264   $215.73   $215.75   $215.70  
  Purchase #5 $204.46   5.212%   $215.1165   $215.12   $215.10   $215.10  
  Purchase #6 $32.79   7.538%   $35.2617   $35.26   $35.25   $35.30  
  Purchase #7 $24.35   8.178%   $26.3413   $26.34   $26.35   $26.30  
  7 purchase totals = $950.57       $1,039.2489   $1,039.25   $1,039.25   $1,039.20