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	$73.42	6.690%	$78.3318	$78.33	$78.35	$78.30
Purchase #2	$114.71	4.857%	$120.2815	$120.28	$120.30	$120.30
Purchase #3	$14.28	3.388%	$14.7638	$14.76	$14.75	$14.80
Purchase #4	$85.82	10.640%	$94.9512	$94.95	$94.95	$95.00
Purchase #5	$23.44	13.463%	$26.5957	$26.60	$26.60	$26.60
Purchase #6	$105.72	5.520%	$111.5557	$111.56	$111.55	$111.60
Purchase #7	$5.73	3.585%	$5.9354	$5.94	$5.95	$5.90
7 purchase totals =	$423.12		$452.4151	$452.42	$452.45	$452.50