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	$54.52	9.738%	$59.8292	$59.83	$59.85	$59.80
Purchase #2	$172.84	10.787%	$191.4843	$191.48	$191.50	$191.50
Purchase #3	$67.71	9.680%	$74.2643	$74.26	$74.25	$74.30
Purchase #4	$142.29	11.708%	$158.9493	$158.95	$158.95	$158.90
Purchase #5	$33.63	5.187%	$35.3744	$35.37	$35.35	$35.40
Purchase #6	$179.76	6.363%	$191.1981	$191.20	$191.20	$191.20
Purchase #7	$53.42	4.204%	$55.6658	$55.67	$55.65	$55.70
7 purchase totals =	$704.17		$766.7654	$766.76	$766.75	$766.80