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	$164.56	9.213%	$179.7209	$179.72	$179.70	$179.70
Purchase #2	$67.65	3.740%	$70.1801	$70.18	$70.20	$70.20
Purchase #3	$135.63	5.559%	$143.1697	$143.17	$143.15	$143.20
Purchase #4	$65.44	13.352%	$74.1775	$74.18	$74.20	$74.20
Purchase #5	$46.31	6.331%	$49.2419	$49.24	$49.25	$49.20
Purchase #6	$111.63	4.561%	$116.7214	$116.72	$116.70	$116.70
Purchase #7	$31.27	9.839%	$34.3467	$34.35	$34.35	$34.30
7 purchase totals =	$622.49		$667.5582	$667.56	$667.55	$667.50