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	$128.97	5.758%	$136.3961	$136.40	$136.40	$136.40
Purchase #2	$101.36	3.804%	$105.2157	$105.22	$105.20	$105.20
Purchase #3	$79.63	3.763%	$82.6265	$82.63	$82.65	$82.60
Purchase #4	$212.54	4.725%	$222.5825	$222.58	$222.60	$222.60
Purchase #5	$171.86	4.197%	$179.073	$179.07	$179.05	$179.10
Purchase #6	$116.37	9.322%	$127.218	$127.22	$127.20	$127.20
Purchase #7	$30.73	8.677%	$33.3964	$33.40	$33.40	$33.40
7 purchase totals =	$841.46		$886.5082	$886.52	$886.50	$886.50