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	$178.64	5.290%	$188.0901	$188.09	$188.10	$188.10
Purchase #2	$159.32	13.381%	$180.6386	$180.64	$180.65	$180.60
Purchase #3	$176.86	11.300%	$196.8452	$196.85	$196.85	$196.80
Purchase #4	$218.72	13.246%	$247.6917	$247.69	$247.70	$247.70
Purchase #5	$125.52	12.713%	$141.4774	$141.48	$141.50	$141.50
Purchase #6	$146.81	4.361%	$153.2124	$153.21	$153.20	$153.20
Purchase #7	$230.52	4.372%	$240.5983	$240.60	$240.60	$240.60
7 purchase totals =	$1,236.39		$1,348.5537	$1,348.56	$1,348.60	$1,348.50