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	$155.38	9.439%	$170.0463	$170.05	$170.05	$170.00
Purchase #2	$168.51	7.817%	$181.6824	$181.68	$181.70	$181.70
Purchase #3	$94.52	3.850%	$98.159	$98.16	$98.15	$98.20
Purchase #4	$103.52	4.804%	$108.4931	$108.49	$108.50	$108.50
Purchase #5	$191.92	11.624%	$214.2288	$214.23	$214.25	$214.20
Purchase #6	$134.33	12.849%	$151.5901	$151.59	$151.60	$151.60
Purchase #7	$243.49	11.636%	$271.8225	$271.82	$271.80	$271.80
7 purchase totals =	$1,091.67		$1,196.0222	$1,196.02	$1,196.05	$1,196.00