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	$43.37	5.429%	$45.7246	$45.72	$45.70	$45.70
Purchase #2	$148.53	11.157%	$165.1015	$165.10	$165.10	$165.10
Purchase #3	$83.81	3.565%	$86.7978	$86.80	$86.80	$86.80
Purchase #4	$148.61	7.210%	$159.3248	$159.32	$159.30	$159.30
Purchase #5	$171.27	3.125%	$176.6222	$176.62	$176.60	$176.60
Purchase #6	$69.28	5.594%	$73.1555	$73.16	$73.15	$73.20
Purchase #7	$129.33	8.114%	$139.8238	$139.82	$139.80	$139.80
7 purchase totals =	$794.20		$846.5502	$846.54	$846.45	$846.50