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	$132.67	11.196%	$147.5237	$147.52	$147.50	$147.50
Purchase #2	$151.79	5.131%	$159.5783	$159.58	$159.60	$159.60
Purchase #3	$246.81	9.713%	$270.7827	$270.78	$270.80	$270.80
Purchase #4	$90.94	10.114%	$100.1377	$100.14	$100.15	$100.10
Purchase #5	$237.77	6.532%	$253.3011	$253.30	$253.30	$253.30
Purchase #6	$86.25	3.286%	$89.0842	$89.08	$89.10	$89.10
Purchase #7	$159.26	10.398%	$175.8199	$175.82	$175.80	$175.80
7 purchase totals =	$1,105.49		$1,196.2276	$1,196.22	$1,196.25	$1,196.20