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	$10.57	9.401%	$11.5637	$11.56	$11.55	$11.60
Purchase #2	$53.55	11.152%	$59.5219	$59.52	$59.50	$59.50
Purchase #3	$17.77	4.164%	$18.5099	$18.51	$18.50	$18.50
Purchase #4	$236.84	3.169%	$244.3455	$244.35	$244.35	$244.30
Purchase #5	$81.65	7.830%	$88.0432	$88.04	$88.05	$88.00
Purchase #6	$141.51	9.297%	$154.6662	$154.67	$154.65	$154.70
Purchase #7	$204.56	5.586%	$215.9867	$215.99	$216.00	$216.00
7 purchase totals =	$746.45		$792.6371	$792.64	$792.60	$792.60