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	$69.62	10.810%	$77.1459	$77.15	$77.15	$77.10
Purchase #2	$93.54	7.696%	$100.7388	$100.74	$100.75	$100.70
Purchase #3	$181.83	4.737%	$190.4433	$190.44	$190.45	$190.40
Purchase #4	$247.52	4.297%	$258.1559	$258.16	$258.15	$258.20
Purchase #5	$39.78	6.822%	$42.4938	$42.49	$42.50	$42.50
Purchase #6	$151.30	13.823%	$172.2142	$172.21	$172.20	$172.20
Purchase #7	$86.29	12.218%	$96.8329	$96.83	$96.85	$96.80
7 purchase totals =	$869.88		$938.0248	$938.02	$938.05	$937.90