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	$163.29	8.467%	$177.1158	$177.12	$177.10	$177.10
Purchase #2	$45.58	3.498%	$47.1744	$47.17	$47.15	$47.20
Purchase #3	$27.60	6.474%	$29.3868	$29.39	$29.40	$29.40
Purchase #4	$65.41	10.792%	$72.469	$72.47	$72.45	$72.50
Purchase #5	$143.71	9.286%	$157.0549	$157.05	$157.05	$157.10
Purchase #6	$64.41	7.627%	$69.3226	$69.32	$69.30	$69.30
Purchase #7	$99.82	11.530%	$111.3292	$111.33	$111.35	$111.30
7 purchase totals =	$609.82		$663.8527	$663.85	$663.80	$663.90