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	$201.43	5.380%	$212.2669	$212.27	$212.25	$212.30
Purchase #2	$14.87	10.650%	$16.4537	$16.45	$16.45	$16.50
Purchase #3	$196.51	7.837%	$211.9105	$211.91	$211.90	$211.90
Purchase #4	$38.45	4.129%	$40.0376	$40.04	$40.05	$40.00
Purchase #5	$99.87	8.694%	$108.5527	$108.55	$108.55	$108.60
Purchase #6	$84.89	5.388%	$89.4639	$89.46	$89.45	$89.50
Purchase #7	$130.49	12.350%	$146.6055	$146.61	$146.60	$146.60
7 purchase totals =	$766.51		$825.2908	$825.29	$825.25	$825.40