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	$235.59	4.457%	$246.0902	$246.09	$246.10	$246.10
Purchase #2	$10.26	13.298%	$11.6244	$11.62	$11.60	$11.60
Purchase #3	$31.57	6.817%	$33.7221	$33.72	$33.70	$33.70
Purchase #4	$99.61	11.760%	$111.3241	$111.32	$111.30	$111.30
Purchase #5	$147.62	13.850%	$168.0654	$168.07	$168.05	$168.10
Purchase #6	$81.97	12.579%	$92.281	$92.28	$92.30	$92.30
Purchase #7	$11.70	5.371%	$12.3284	$12.33	$12.35	$12.30
7 purchase totals =	$618.32		$675.4356	$675.43	$675.40	$675.40