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	$163.61	4.391%	$170.7941	$170.79	$170.80	$170.80
Purchase #2	$98.77	12.636%	$111.2506	$111.25	$111.25	$111.30
Purchase #3	$214.49	8.694%	$233.1378	$233.14	$233.15	$233.10
Purchase #4	$52.46	11.490%	$58.4877	$58.49	$58.50	$58.50
Purchase #5	$117.31	12.145%	$131.5573	$131.56	$131.55	$131.60
Purchase #6	$44.73	3.325%	$46.2173	$46.22	$46.20	$46.20
Purchase #7	$11.37	13.555%	$12.9112	$12.91	$12.90	$12.90
7 purchase totals =	$702.74		$764.3560	$764.36	$764.35	$764.40