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	$203.57	12.742%	$229.5089	$229.51	$229.50	$229.50
Purchase #2	$137.27	11.574%	$153.1576	$153.16	$153.15	$153.20
Purchase #3	$220.31	12.634%	$248.144	$248.14	$248.15	$248.10
Purchase #4	$36.33	3.243%	$37.5082	$37.51	$37.50	$37.50
Purchase #5	$195.72	9.659%	$214.6246	$214.62	$214.60	$214.60
Purchase #6	$44.51	7.707%	$47.9404	$47.94	$47.95	$47.90
Purchase #7	$151.71	4.630%	$158.7342	$158.73	$158.75	$158.70
7 purchase totals =	$989.42		$1,089.6179	$1,089.61	$1,089.60	$1,089.50