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	$93.82	7.258%	$100.6295	$100.63	$100.65	$100.60
Purchase #2	$18.76	4.519%	$19.6078	$19.61	$19.60	$19.60
Purchase #3	$200.30	3.717%	$207.7452	$207.75	$207.75	$207.70
Purchase #4	$20.60	5.631%	$21.76	$21.76	$21.75	$21.80
Purchase #5	$229.67	5.603%	$242.5384	$242.54	$242.55	$242.50
Purchase #6	$57.51	6.815%	$61.4293	$61.43	$61.45	$61.40
Purchase #7	$58.52	6.227%	$62.164	$62.16	$62.15	$62.20
7 purchase totals =	$679.18		$715.8742	$715.88	$715.90	$715.80