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	$132.83	13.270%	$150.4565	$150.46	$150.45	$150.50
Purchase #2	$9.40	8.658%	$10.2139	$10.21	$10.20	$10.20
Purchase #3	$48.40	4.166%	$50.4163	$50.42	$50.40	$50.40
Purchase #4	$102.27	5.763%	$108.1638	$108.16	$108.15	$108.20
Purchase #5	$207.26	13.137%	$234.4877	$234.49	$234.50	$234.50
Purchase #6	$73.37	9.700%	$80.4869	$80.49	$80.50	$80.50
Purchase #7	$96.80	7.299%	$103.8654	$103.87	$103.85	$103.90
7 purchase totals =	$670.33		$738.0905	$738.10	$738.05	$738.20