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	$185.41	7.503%	$199.3213	$199.32	$199.30	$199.30
Purchase #2	$90.28	6.228%	$95.9026	$95.90	$95.90	$95.90
Purchase #3	$111.28	4.814%	$116.637	$116.64	$116.65	$116.60
Purchase #4	$113.35	12.568%	$127.5958	$127.60	$127.60	$127.60
Purchase #5	$13.77	7.278%	$14.7722	$14.77	$14.75	$14.80
Purchase #6	$101.80	9.799%	$111.7754	$111.78	$111.80	$111.80
Purchase #7	$134.72	12.157%	$151.0979	$151.10	$151.10	$151.10
7 purchase totals =	$750.61		$817.1022	$817.11	$817.10	$817.10