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	$166.38	5.222%	$175.0684	$175.07	$175.05	$175.10
Purchase #2	$49.27	11.858%	$55.1124	$55.11	$55.10	$55.10
Purchase #3	$177.58	5.604%	$187.5316	$187.53	$187.55	$187.50
Purchase #4	$176.41	11.340%	$196.4149	$196.41	$196.40	$196.40
Purchase #5	$191.48	8.851%	$208.4279	$208.43	$208.45	$208.40
Purchase #6	$90.41	10.105%	$99.5459	$99.55	$99.55	$99.50
Purchase #7	$31.66	4.314%	$33.0258	$33.03	$33.05	$33.00
7 purchase totals =	$883.19		$955.1269	$955.13	$955.15	$955.00