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	$89.58	6.222%	$95.1537	$95.15	$95.15	$95.20
Purchase #2	$118.45	7.245%	$127.0317	$127.03	$127.05	$127.00
Purchase #3	$232.87	9.443%	$254.8599	$254.86	$254.85	$254.90
Purchase #4	$188.91	10.273%	$208.3167	$208.32	$208.30	$208.30
Purchase #5	$28.49	13.205%	$32.2521	$32.25	$32.25	$32.30
Purchase #6	$113.58	4.287%	$118.4492	$118.45	$118.45	$118.40
Purchase #7	$208.42	8.606%	$226.3566	$226.36	$226.35	$226.40
7 purchase totals =	$980.30		$1,062.4199	$1,062.42	$1,062.40	$1,062.50