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	$233.82	9.658%	$256.4023	$256.40	$256.40	$256.40
Purchase #2	$149.76	3.678%	$155.2682	$155.27	$155.25	$155.30
Purchase #3	$86.62	10.428%	$95.6527	$95.65	$95.65	$95.70
Purchase #4	$146.70	3.653%	$152.059	$152.06	$152.05	$152.10
Purchase #5	$187.69	6.430%	$199.7585	$199.76	$199.75	$199.80
Purchase #6	$232.60	3.786%	$241.4062	$241.41	$241.40	$241.40
Purchase #7	$178.89	12.322%	$200.9328	$200.93	$200.95	$200.90
7 purchase totals =	$1,216.08		$1,301.4797	$1,301.48	$1,301.45	$1,301.60