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	$218.73	13.153%	$247.4996	$247.50	$247.50	$247.50
Purchase #2	$67.71	7.634%	$72.879	$72.88	$72.90	$72.90
Purchase #3	$205.63	4.860%	$215.6236	$215.62	$215.60	$215.60
Purchase #4	$11.68	5.248%	$12.293	$12.29	$12.30	$12.30
Purchase #5	$155.86	11.568%	$173.8899	$173.89	$173.90	$173.90
Purchase #6	$114.84	13.700%	$130.5731	$130.57	$130.55	$130.60
Purchase #7	$202.84	6.139%	$215.2923	$215.29	$215.30	$215.30
7 purchase totals =	$977.29		$1,068.0505	$1,068.04	$1,068.05	$1,068.10