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	$99.98	5.125%	$105.104	$105.10	$105.10	$105.10
Purchase #2	$174.91	5.468%	$184.4741	$184.47	$184.45	$184.50
Purchase #3	$189.58	6.464%	$201.8345	$201.83	$201.85	$201.80
Purchase #4	$111.89	13.534%	$127.0332	$127.03	$127.05	$127.00
Purchase #5	$152.55	3.820%	$158.3774	$158.38	$158.40	$158.40
Purchase #6	$71.45	8.770%	$77.7162	$77.72	$77.70	$77.70
Purchase #7	$69.90	11.162%	$77.7022	$77.70	$77.70	$77.70
7 purchase totals =	$870.26		$932.2416	$932.23	$932.25	$932.20