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	$248.69	3.495%	$257.3817	$257.38	$257.40	$257.40
Purchase #2	$204.51	10.171%	$225.3107	$225.31	$225.30	$225.30
Purchase #3	$175.34	3.524%	$181.519	$181.52	$181.50	$181.50
Purchase #4	$149.94	10.333%	$165.4333	$165.43	$165.45	$165.40
Purchase #5	$221.78	8.760%	$241.2079	$241.21	$241.20	$241.20
Purchase #6	$49.32	12.108%	$55.2917	$55.29	$55.30	$55.30
Purchase #7	$212.39	13.680%	$241.445	$241.45	$241.45	$241.40
7 purchase totals =	$1,261.97		$1,367.5893	$1,367.59	$1,367.60	$1,367.50