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	$248.26	6.119%	$263.451	$263.45	$263.45	$263.50
Purchase #2	$112.72	13.700%	$128.1626	$128.16	$128.15	$128.20
Purchase #3	$200.37	13.868%	$228.1573	$228.16	$228.15	$228.20
Purchase #4	$165.53	3.381%	$171.1266	$171.13	$171.15	$171.10
Purchase #5	$161.88	7.168%	$173.4836	$173.48	$173.50	$173.50
Purchase #6	$139.92	13.447%	$158.735	$158.74	$158.75	$158.70
Purchase #7	$10.65	5.433%	$11.2286	$11.23	$11.25	$11.20
7 purchase totals =	$1,039.33		$1,134.3447	$1,134.35	$1,134.40	$1,134.40