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	$127.37	11.198%	$141.6329	$141.63	$141.65	$141.60
Purchase #2	$103.66	5.810%	$109.6826	$109.68	$109.70	$109.70
Purchase #3	$38.98	4.345%	$40.6737	$40.67	$40.65	$40.70
Purchase #4	$97.38	3.449%	$100.7386	$100.74	$100.75	$100.70
Purchase #5	$93.99	11.826%	$105.1053	$105.11	$105.10	$105.10
Purchase #6	$37.32	6.752%	$39.8398	$39.84	$39.85	$39.80
Purchase #7	$22.53	10.213%	$24.831	$24.83	$24.85	$24.80
7 purchase totals =	$521.23		$562.5039	$562.50	$562.55	$562.40