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	$203.51	10.236%	$224.3413	$224.34	$224.35	$224.30
Purchase #2	$50.46	5.119%	$53.043	$53.04	$53.05	$53.00
Purchase #3	$84.85	8.410%	$91.9859	$91.99	$92.00	$92.00
Purchase #4	$99.61	12.157%	$111.7196	$111.72	$111.70	$111.70
Purchase #5	$137.51	12.874%	$155.213	$155.21	$155.20	$155.20
Purchase #6	$12.40	11.175%	$13.7857	$13.79	$13.80	$13.80
Purchase #7	$49.38	11.653%	$55.1343	$55.13	$55.15	$55.10
7 purchase totals =	$637.72		$705.2228	$705.22	$705.25	$705.10