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 $48.64   3.226%   $50.2091   $50.21   $50.20   $50.20  
  Purchase #2 $244.51   3.872%   $253.9774   $253.98   $254.00   $254.00  
  Purchase #3 $224.74   3.137%   $231.7901   $231.79   $231.80   $231.80  
  Purchase #4 $96.88   6.246%   $102.9311   $102.93   $102.95   $102.90  
  Purchase #5 $126.82   13.505%   $143.947   $143.95   $143.95   $143.90  
  Purchase #6 $11.68   4.628%   $12.2206   $12.22   $12.20   $12.20  
  Purchase #7 $184.64   8.306%   $199.9762   $199.98   $200.00   $200.00  
  7 purchase totals = $937.91       $995.0515   $995.06   $995.10   $995.00