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	$168.88	11.817%	$188.8365	$188.84	$188.85	$188.80
Purchase #2	$125.69	9.480%	$137.6054	$137.61	$137.60	$137.60
Purchase #3	$214.84	3.810%	$223.0254	$223.03	$223.05	$223.00
Purchase #4	$5.92	6.503%	$6.305	$6.31	$6.30	$6.30
Purchase #5	$101.57	3.495%	$105.1199	$105.12	$105.10	$105.10
Purchase #6	$34.88	6.624%	$37.1905	$37.19	$37.20	$37.20
Purchase #7	$242.52	11.764%	$271.0501	$271.05	$271.05	$271.10
7 purchase totals =	$894.30		$969.1328	$969.15	$969.15	$969.10