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 $36.48   13.658%   $41.4624   $41.46   $41.45   $41.50  
  Purchase #2 $119.42   12.490%   $134.3356   $134.34   $134.35   $134.30  
  Purchase #3 $245.86   8.566%   $266.9204   $266.92   $266.90   $266.90  
  Purchase #4 $88.79   9.108%   $96.877   $96.88   $96.90   $96.90  
  Purchase #5 $141.74   3.140%   $146.1906   $146.19   $146.20   $146.20  
  Purchase #6 $67.25   12.110%   $75.394   $75.39   $75.40   $75.40  
  Purchase #7 $176.95   8.763%   $192.4561   $192.46   $192.45   $192.50  
  7 purchase totals = $876.49       $953.6361   $953.64   $953.65   $953.70