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 $212.39   13.698%   $241.4832   $241.48   $241.50   $241.50  
  Purchase #2 $8.86   9.399%   $9.6928   $9.69   $9.70   $9.70  
  Purchase #3 $210.27   9.844%   $230.969   $230.97   $230.95   $231.00  
  Purchase #4 $85.86   7.695%   $92.4669   $92.47   $92.45   $92.50  
  Purchase #5 $246.45   5.591%   $260.229   $260.23   $260.25   $260.20  
  Purchase #6 $174.97   4.340%   $182.5637   $182.56   $182.55   $182.60  
  Purchase #7 $156.27   9.200%   $170.6468   $170.65   $170.65   $170.60  
  7 purchase totals = $1,095.07       $1,188.0514   $1,188.05   $1,188.05   $1,188.10