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	$88.51	7.210%	$94.8916	$94.89	$94.90	$94.90
Purchase #2	$62.63	7.440%	$67.2897	$67.29	$67.30	$67.30
Purchase #3	$235.43	8.573%	$255.6134	$255.61	$255.60	$255.60
Purchase #4	$92.37	8.852%	$100.5466	$100.55	$100.55	$100.50
Purchase #5	$239.72	7.607%	$257.9555	$257.96	$257.95	$258.00
Purchase #6	$80.81	13.549%	$91.7589	$91.76	$91.75	$91.80
Purchase #7	$107.55	4.763%	$112.6726	$112.67	$112.65	$112.70
7 purchase totals =	$907.02		$980.7283	$980.73	$980.70	$980.80