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	$29.61	3.424%	$30.6238	$30.62	$30.60	$30.60
Purchase #2	$154.33	12.555%	$173.7061	$173.71	$173.70	$173.70
Purchase #3	$172.52	13.777%	$196.2881	$196.29	$196.30	$196.30
Purchase #4	$32.81	13.408%	$37.2092	$37.21	$37.20	$37.20
Purchase #5	$237.88	13.401%	$269.7583	$269.76	$269.75	$269.80
Purchase #6	$37.25	11.563%	$41.5572	$41.56	$41.55	$41.60
Purchase #7	$218.69	3.848%	$227.1052	$227.11	$227.10	$227.10
7 purchase totals =	$883.09		$976.2479	$976.26	$976.20	$976.30