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	$12.76	4.187%	$13.2943	$13.29	$13.30	$13.30
Purchase #2	$20.60	9.252%	$22.5059	$22.51	$22.50	$22.50
Purchase #3	$59.59	13.275%	$67.5006	$67.50	$67.50	$67.50
Purchase #4	$52.73	7.682%	$56.7807	$56.78	$56.80	$56.80
Purchase #5	$152.64	3.171%	$157.4802	$157.48	$157.50	$157.50
Purchase #6	$227.91	9.181%	$248.8344	$248.83	$248.85	$248.80
Purchase #7	$163.45	5.475%	$172.3989	$172.40	$172.40	$172.40
7 purchase totals =	$689.68		$738.7950	$738.79	$738.85	$738.80