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	$231.96	4.483%	$242.3588	$242.36	$242.35	$242.40
Purchase #2	$249.34	10.530%	$275.5955	$275.60	$275.60	$275.60
Purchase #3	$40.74	12.716%	$45.9205	$45.92	$45.90	$45.90
Purchase #4	$50.49	11.181%	$56.1353	$56.14	$56.15	$56.10
Purchase #5	$177.53	12.129%	$199.0626	$199.06	$199.05	$199.10
Purchase #6	$29.37	9.543%	$32.1728	$32.17	$32.15	$32.20
Purchase #7	$155.64	5.500%	$164.2002	$164.20	$164.20	$164.20
7 purchase totals =	$935.07		$1,015.4457	$1,015.45	$1,015.40	$1,015.50