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	$212.61	13.489%	$241.289	$241.29	$241.30	$241.30
Purchase #2	$156.33	11.201%	$173.8405	$173.84	$173.85	$173.80
Purchase #3	$250.79	10.585%	$277.3361	$277.34	$277.35	$277.30
Purchase #4	$80.89	12.793%	$91.2383	$91.24	$91.25	$91.20
Purchase #5	$158.75	4.290%	$165.5604	$165.56	$165.55	$165.60
Purchase #6	$43.64	11.412%	$48.6202	$48.62	$48.60	$48.60
Purchase #7	$39.78	9.462%	$43.544	$43.54	$43.55	$43.50
7 purchase totals =	$942.79		$1,041.4285	$1,041.43	$1,041.45	$1,041.30