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	$100.88	10.282%	$111.2525	$111.25	$111.25	$111.30
Purchase #2	$39.89	7.444%	$42.8594	$42.86	$42.85	$42.90
Purchase #3	$118.50	12.205%	$132.9629	$132.96	$132.95	$133.00
Purchase #4	$35.31	5.121%	$37.1182	$37.12	$37.10	$37.10
Purchase #5	$55.72	13.129%	$63.0355	$63.04	$63.05	$63.00
Purchase #6	$223.26	9.519%	$244.5121	$244.51	$244.50	$244.50
Purchase #7	$235.88	11.391%	$262.7491	$262.75	$262.75	$262.70
7 purchase totals =	$809.44		$894.4897	$894.49	$894.45	$894.50