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 $115.61   8.590%   $125.5409   $125.54   $125.55   $125.50  
  Purchase #2 $89.98   4.191%   $93.7511   $93.75   $93.75   $93.80  
  Purchase #3 $75.65   11.678%   $84.4844   $84.48   $84.50   $84.50  
  Purchase #4 $56.28   11.866%   $62.9582   $62.96   $62.95   $63.00  
  Purchase #5 $202.46   7.402%   $217.4461   $217.45   $217.45   $217.40  
  Purchase #6 $212.29   5.631%   $224.244   $224.24   $224.25   $224.20  
  Purchase #7 $224.40   7.520%   $241.2749   $241.27   $241.25   $241.30  
  7 purchase totals = $976.67       $1,049.6996   $1,049.69   $1,049.70   $1,049.70