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	$210.58	10.142%	$231.937	$231.94	$231.95	$231.90
Purchase #2	$127.98	8.350%	$138.6663	$138.67	$138.65	$138.70
Purchase #3	$197.36	5.630%	$208.4714	$208.47	$208.45	$208.50
Purchase #4	$155.33	10.130%	$171.0649	$171.06	$171.05	$171.10
Purchase #5	$144.72	9.308%	$158.1905	$158.19	$158.20	$158.20
Purchase #6	$91.79	10.595%	$101.5152	$101.52	$101.50	$101.50
Purchase #7	$85.69	4.219%	$89.3053	$89.31	$89.30	$89.30
7 purchase totals =	$1,013.45		$1,099.1506	$1,099.16	$1,099.10	$1,099.20