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	$203.70	10.655%	$225.4042	$225.40	$225.40	$225.40
Purchase #2	$9.81	6.702%	$10.4675	$10.47	$10.45	$10.50
Purchase #3	$129.95	7.301%	$139.4376	$139.44	$139.45	$139.40
Purchase #4	$174.45	6.300%	$185.4404	$185.44	$185.45	$185.40
Purchase #5	$181.60	4.707%	$190.1479	$190.15	$190.15	$190.10
Purchase #6	$90.86	7.541%	$97.7118	$97.71	$97.70	$97.70
Purchase #7	$226.89	13.200%	$256.8395	$256.84	$256.85	$256.80
7 purchase totals =	$1,017.26		$1,105.4489	$1,105.45	$1,105.45	$1,105.30