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	$9.73	8.819%	$10.5881	$10.59	$10.60	$10.60
Purchase #2	$216.59	4.294%	$225.8904	$225.89	$225.90	$225.90
Purchase #3	$79.68	13.681%	$90.581	$90.58	$90.60	$90.60
Purchase #4	$16.51	6.670%	$17.6112	$17.61	$17.60	$17.60
Purchase #5	$115.77	12.168%	$129.8569	$129.86	$129.85	$129.90
Purchase #6	$92.91	9.415%	$101.6575	$101.66	$101.65	$101.70
Purchase #7	$155.96	5.871%	$165.1164	$165.12	$165.10	$165.10
7 purchase totals =	$687.15		$741.3015	$741.31	$741.30	$741.40