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	$232.33	10.256%	$256.1578	$256.16	$256.15	$256.20
Purchase #2	$65.60	11.326%	$73.0299	$73.03	$73.05	$73.00
Purchase #3	$128.32	6.825%	$137.0778	$137.08	$137.10	$137.10
Purchase #4	$33.27	11.702%	$37.1633	$37.16	$37.15	$37.20
Purchase #5	$157.78	13.556%	$179.1687	$179.17	$179.15	$179.20
Purchase #6	$208.31	12.671%	$234.705	$234.71	$234.70	$234.70
Purchase #7	$145.85	6.588%	$155.4586	$155.46	$155.45	$155.50
7 purchase totals =	$971.46		$1,072.7611	$1,072.77	$1,072.75	$1,072.90