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	$190.91	9.215%	$208.5024	$208.50	$208.50	$208.50
Purchase #2	$134.61	4.264%	$140.3498	$140.35	$140.35	$140.30
Purchase #3	$99.54	13.763%	$113.2397	$113.24	$113.25	$113.20
Purchase #4	$158.42	8.331%	$171.618	$171.62	$171.60	$171.60
Purchase #5	$230.44	4.317%	$240.3881	$240.39	$240.40	$240.40
Purchase #6	$165.62	4.291%	$172.7268	$172.73	$172.75	$172.70
Purchase #7	$35.54	4.201%	$37.033	$37.03	$37.05	$37.00
7 purchase totals =	$1,015.08		$1,083.8578	$1,083.86	$1,083.90	$1,083.70