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	$100.60	8.669%	$109.321	$109.32	$109.30	$109.30
Purchase #2	$10.66	13.482%	$12.0972	$12.10	$12.10	$12.10
Purchase #3	$43.58	5.234%	$45.861	$45.86	$45.85	$45.90
Purchase #4	$27.27	4.341%	$28.4538	$28.45	$28.45	$28.50
Purchase #5	$246.78	5.220%	$259.6619	$259.66	$259.65	$259.70
Purchase #6	$194.62	11.245%	$216.505	$216.51	$216.50	$216.50
Purchase #7	$55.91	13.526%	$63.4724	$63.47	$63.45	$63.50
7 purchase totals =	$679.42		$735.3723	$735.37	$735.30	$735.50