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	$100.75	12.273%	$113.115	$113.12	$113.10	$113.10
Purchase #2	$69.36	12.720%	$78.1826	$78.18	$78.20	$78.20
Purchase #3	$87.71	13.839%	$99.8482	$99.85	$99.85	$99.80
Purchase #4	$118.88	8.799%	$129.3403	$129.34	$129.35	$129.30
Purchase #5	$128.35	3.251%	$132.5227	$132.52	$132.50	$132.50
Purchase #6	$152.31	4.790%	$159.6056	$159.61	$159.60	$159.60
Purchase #7	$17.78	10.749%	$19.6912	$19.69	$19.70	$19.70
7 purchase totals =	$675.14		$732.3056	$732.31	$732.30	$732.20