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	$221.78	9.725%	$243.3481	$243.35	$243.35	$243.30
Purchase #2	$85.89	4.396%	$89.6657	$89.67	$89.65	$89.70
Purchase #3	$35.68	11.701%	$39.8549	$39.85	$39.85	$39.90
Purchase #4	$45.88	6.287%	$48.7645	$48.76	$48.75	$48.80
Purchase #5	$21.66	3.646%	$22.4497	$22.45	$22.45	$22.40
Purchase #6	$12.66	7.277%	$13.5813	$13.58	$13.60	$13.60
Purchase #7	$157.91	13.723%	$179.58	$179.58	$179.60	$179.60
7 purchase totals =	$581.46		$637.2442	$637.24	$637.25	$637.30