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	$83.85	13.758%	$95.3861	$95.39	$95.40	$95.40
Purchase #2	$173.56	11.717%	$193.896	$193.90	$193.90	$193.90
Purchase #3	$99.81	11.294%	$111.0825	$111.08	$111.10	$111.10
Purchase #4	$63.48	4.738%	$66.4877	$66.49	$66.50	$66.50
Purchase #5	$43.57	4.561%	$45.5572	$45.56	$45.55	$45.60
Purchase #6	$197.80	7.297%	$212.2335	$212.23	$212.25	$212.20
Purchase #7	$77.40	3.820%	$80.3567	$80.36	$80.35	$80.40
7 purchase totals =	$739.47		$804.9997	$805.01	$805.05	$805.10