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	$156.95	9.791%	$172.317	$172.32	$172.30	$172.30
Purchase #2	$128.29	10.540%	$141.8118	$141.81	$141.80	$141.80
Purchase #3	$112.66	13.332%	$127.6798	$127.68	$127.70	$127.70
Purchase #4	$225.58	6.732%	$240.766	$240.77	$240.75	$240.80
Purchase #5	$246.52	13.424%	$279.6128	$279.61	$279.60	$279.60
Purchase #6	$241.43	11.651%	$269.559	$269.56	$269.55	$269.60
Purchase #7	$30.88	3.857%	$32.071	$32.07	$32.05	$32.10
7 purchase totals =	$1,142.31		$1,263.8174	$1,263.82	$1,263.75	$1,263.90