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	$131.64	11.639%	$146.9616	$146.96	$146.95	$147.00
Purchase #2	$57.80	7.708%	$62.2552	$62.26	$62.25	$62.30
Purchase #3	$190.64	4.171%	$198.5916	$198.59	$198.60	$198.60
Purchase #4	$117.74	11.137%	$130.8527	$130.85	$130.85	$130.90
Purchase #5	$223.67	6.748%	$238.7633	$238.76	$238.75	$238.80
Purchase #6	$137.89	5.237%	$145.1113	$145.11	$145.10	$145.10
Purchase #7	$86.84	8.325%	$94.0694	$94.07	$94.05	$94.10
7 purchase totals =	$946.22		$1,016.6051	$1,016.60	$1,016.55	$1,016.80