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	$159.87	4.830%	$167.5917	$167.59	$167.60	$167.60
Purchase #2	$41.82	9.548%	$45.813	$45.81	$45.80	$45.80
Purchase #3	$105.89	5.499%	$111.7129	$111.71	$111.70	$111.70
Purchase #4	$19.49	10.737%	$21.5826	$21.58	$21.60	$21.60
Purchase #5	$250.58	9.662%	$274.791	$274.79	$274.80	$274.80
Purchase #6	$74.26	12.552%	$83.5811	$83.58	$83.60	$83.60
Purchase #7	$156.39	3.307%	$161.5618	$161.56	$161.55	$161.60
7 purchase totals =	$808.30		$866.6341	$866.62	$866.65	$866.70