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	$172.25	7.777%	$185.6459	$185.65	$185.65	$185.60
Purchase #2	$5.26	12.462%	$5.9155	$5.92	$5.90	$5.90
Purchase #3	$153.58	5.556%	$162.1129	$162.11	$162.10	$162.10
Purchase #4	$32.70	10.344%	$36.0825	$36.08	$36.10	$36.10
Purchase #5	$162.36	6.225%	$172.4669	$172.47	$172.45	$172.50
Purchase #6	$171.52	10.243%	$189.0888	$189.09	$189.10	$189.10
Purchase #7	$217.29	4.519%	$227.1093	$227.11	$227.10	$227.10
7 purchase totals =	$914.96		$978.4218	$978.43	$978.40	$978.40