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 $214.38   10.238%   $236.3282   $236.33   $236.35   $236.30  
  Purchase #2 $242.54   13.146%   $274.4243   $274.42   $274.40   $274.40  
  Purchase #3 $41.80   4.121%   $43.5226   $43.52   $43.50   $43.50  
  Purchase #4 $64.77   5.418%   $68.2792   $68.28   $68.30   $68.30  
  Purchase #5 $58.27   13.800%   $66.3113   $66.31   $66.30   $66.30  
  Purchase #6 $201.62   12.103%   $226.0221   $226.02   $226.00   $226.00  
  Purchase #7 $32.73   6.796%   $34.9543   $34.95   $34.95   $35.00  
  7 purchase totals = $856.11       $949.8420   $949.83   $949.80   $949.80