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	$33.91	6.211%	$36.0162	$36.02	$36.00	$36.00
Purchase #2	$118.94	9.348%	$130.0585	$130.06	$130.05	$130.10
Purchase #3	$37.66	8.422%	$40.8317	$40.83	$40.85	$40.80
Purchase #4	$130.83	8.285%	$141.6693	$141.67	$141.65	$141.70
Purchase #5	$43.90	12.229%	$49.2685	$49.27	$49.25	$49.30
Purchase #6	$101.56	11.865%	$113.6101	$113.61	$113.60	$113.60
Purchase #7	$197.68	12.542%	$222.473	$222.47	$222.45	$222.50
7 purchase totals =	$664.48		$733.9273	$733.93	$733.85	$734.00