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	$88.69	5.590%	$93.6478	$93.65	$93.65	$93.60
Purchase #2	$54.30	12.579%	$61.1304	$61.13	$61.15	$61.10
Purchase #3	$18.43	11.392%	$20.5295	$20.53	$20.55	$20.50
Purchase #4	$198.96	4.738%	$208.3867	$208.39	$208.40	$208.40
Purchase #5	$242.63	5.711%	$256.4866	$256.49	$256.50	$256.50
Purchase #6	$35.27	8.626%	$38.3124	$38.31	$38.30	$38.30
Purchase #7	$71.77	6.105%	$76.1516	$76.15	$76.15	$76.20
7 purchase totals =	$710.05		$754.6450	$754.65	$754.70	$754.60