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	$207.37	10.207%	$228.5363	$228.54	$228.55	$228.50
Purchase #2	$52.69	3.460%	$54.5131	$54.51	$54.50	$54.50
Purchase #3	$212.32	12.832%	$239.5649	$239.56	$239.55	$239.60
Purchase #4	$140.76	12.738%	$158.69	$158.69	$158.70	$158.70
Purchase #5	$83.82	7.634%	$90.2188	$90.22	$90.20	$90.20
Purchase #6	$106.84	11.250%	$118.8595	$118.86	$118.85	$118.90
Purchase #7	$77.62	13.753%	$88.2951	$88.30	$88.30	$88.30
7 purchase totals =	$881.42		$978.6777	$978.68	$978.65	$978.70