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	$236.64	7.110%	$253.4651	$253.47	$253.45	$253.50
Purchase #2	$207.82	3.244%	$214.5617	$214.56	$214.55	$214.60
Purchase #3	$105.80	6.473%	$112.6484	$112.65	$112.65	$112.60
Purchase #4	$132.76	8.110%	$143.5268	$143.53	$143.55	$143.50
Purchase #5	$171.52	11.673%	$191.5415	$191.54	$191.55	$191.50
Purchase #6	$223.72	13.653%	$254.2645	$254.26	$254.25	$254.30
Purchase #7	$40.34	13.606%	$45.8287	$45.83	$45.85	$45.80
7 purchase totals =	$1,118.60		$1,215.8367	$1,215.84	$1,215.85	$1,215.80