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	$107.50	3.659%	$111.4334	$111.43	$111.45	$111.40
Purchase #2	$35.43	6.226%	$37.6359	$37.64	$37.65	$37.60
Purchase #3	$45.98	8.269%	$49.7821	$49.78	$49.80	$49.80
Purchase #4	$156.35	10.160%	$172.2352	$172.24	$172.25	$172.20
Purchase #5	$61.85	13.755%	$70.3575	$70.36	$70.35	$70.40
Purchase #6	$132.25	7.566%	$142.256	$142.26	$142.25	$142.30
Purchase #7	$165.65	5.838%	$175.3206	$175.32	$175.30	$175.30
7 purchase totals =	$705.01		$759.0207	$759.03	$759.05	$759.00