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	$220.41	8.324%	$238.7569	$238.76	$238.75	$238.80
Purchase #2	$10.86	9.542%	$11.8963	$11.90	$11.90	$11.90
Purchase #3	$92.32	9.213%	$100.8254	$100.83	$100.85	$100.80
Purchase #4	$247.30	10.205%	$272.537	$272.54	$272.55	$272.50
Purchase #5	$131.51	7.753%	$141.706	$141.71	$141.70	$141.70
Purchase #6	$25.82	5.597%	$27.2651	$27.27	$27.25	$27.30
Purchase #7	$9.38	13.344%	$10.6317	$10.63	$10.65	$10.60
7 purchase totals =	$737.60		$803.6184	$803.64	$803.65	$803.60