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	$200.37	11.826%	$224.0658	$224.07	$224.05	$224.10
Purchase #2	$43.85	7.450%	$47.1168	$47.12	$47.10	$47.10
Purchase #3	$173.81	6.672%	$185.4066	$185.41	$185.40	$185.40
Purchase #4	$97.72	10.566%	$108.0451	$108.05	$108.05	$108.00
Purchase #5	$142.76	9.155%	$155.8297	$155.83	$155.85	$155.80
Purchase #6	$240.94	9.766%	$264.4702	$264.47	$264.45	$264.50
Purchase #7	$160.63	3.530%	$166.3002	$166.30	$166.30	$166.30
7 purchase totals =	$1,060.08		$1,151.2344	$1,151.25	$1,151.20	$1,151.20