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	$58.40	5.684%	$61.7195	$61.72	$61.70	$61.70
Purchase #2	$190.84	4.163%	$198.7847	$198.78	$198.80	$198.80
Purchase #3	$53.85	10.137%	$59.3088	$59.31	$59.30	$59.30
Purchase #4	$36.79	5.209%	$38.7064	$38.71	$38.70	$38.70
Purchase #5	$88.68	13.335%	$100.5055	$100.51	$100.50	$100.50
Purchase #6	$230.31	5.433%	$242.8227	$242.82	$242.80	$242.80
Purchase #7	$35.31	7.472%	$37.9484	$37.95	$37.95	$37.90
7 purchase totals =	$694.18		$739.7960	$739.80	$739.75	$739.70