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	$130.62	12.404%	$146.8221	$146.82	$146.80	$146.80
Purchase #2	$127.45	4.268%	$132.8896	$132.89	$132.90	$132.90
Purchase #3	$144.85	13.869%	$164.9392	$164.94	$164.95	$164.90
Purchase #4	$62.58	12.388%	$70.3324	$70.33	$70.35	$70.30
Purchase #5	$204.29	13.834%	$232.5515	$232.55	$232.55	$232.60
Purchase #6	$36.60	11.277%	$40.7274	$40.73	$40.75	$40.70
Purchase #7	$147.41	4.242%	$153.6631	$153.66	$153.65	$153.70
7 purchase totals =	$853.80		$941.9253	$941.92	$941.95	$941.90