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	$110.89	13.414%	$125.7648	$125.76	$125.75	$125.80
Purchase #2	$56.90	9.354%	$62.2224	$62.22	$62.20	$62.20
Purchase #3	$88.66	3.419%	$91.6913	$91.69	$91.70	$91.70
Purchase #4	$100.72	10.782%	$111.5796	$111.58	$111.60	$111.60
Purchase #5	$48.41	11.530%	$53.9917	$53.99	$54.00	$54.00
Purchase #6	$130.38	13.832%	$148.4142	$148.41	$148.40	$148.40
Purchase #7	$118.50	10.742%	$131.2293	$131.23	$131.25	$131.20
7 purchase totals =	$654.46		$724.8933	$724.88	$724.90	$724.90