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	$88.32	4.485%	$92.2812	$92.28	$92.30	$92.30
Purchase #2	$219.70	8.385%	$238.1218	$238.12	$238.10	$238.10
Purchase #3	$61.50	7.791%	$66.2915	$66.29	$66.30	$66.30
Purchase #4	$103.89	13.818%	$118.2455	$118.25	$118.25	$118.20
Purchase #5	$89.42	8.279%	$96.8231	$96.82	$96.80	$96.80
Purchase #6	$49.47	9.321%	$54.0811	$54.08	$54.10	$54.10
Purchase #7	$221.98	3.644%	$230.069	$230.07	$230.05	$230.10
7 purchase totals =	$834.28		$895.9132	$895.91	$895.90	$895.90