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	$172.84	5.570%	$182.4672	$182.47	$182.45	$182.50
Purchase #2	$29.77	9.406%	$32.5702	$32.57	$32.55	$32.60
Purchase #3	$48.85	7.722%	$52.6222	$52.62	$52.60	$52.60
Purchase #4	$60.40	7.834%	$65.1317	$65.13	$65.15	$65.10
Purchase #5	$93.77	12.107%	$105.1227	$105.12	$105.10	$105.10
Purchase #6	$19.82	5.105%	$20.8318	$20.83	$20.85	$20.80
Purchase #7	$90.95	11.824%	$101.7039	$101.70	$101.70	$101.70
7 purchase totals =	$516.40		$560.4497	$560.44	$560.40	$560.40