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	$247.85	11.228%	$275.6786	$275.68	$275.70	$275.70
Purchase #2	$39.47	10.747%	$43.7118	$43.71	$43.70	$43.70
Purchase #3	$222.51	3.759%	$230.8742	$230.87	$230.85	$230.90
Purchase #4	$58.42	12.748%	$65.8674	$65.87	$65.85	$65.90
Purchase #5	$89.31	5.710%	$94.4096	$94.41	$94.40	$94.40
Purchase #6	$34.40	11.741%	$38.4389	$38.44	$38.45	$38.40
Purchase #7	$223.73	13.805%	$254.6159	$254.62	$254.60	$254.60
7 purchase totals =	$915.69		$1,003.5964	$1,003.60	$1,003.55	$1,003.60