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	$223.98	4.406%	$233.8486	$233.85	$233.85	$233.80
Purchase #2	$158.91	7.164%	$170.2943	$170.29	$170.30	$170.30
Purchase #3	$93.50	11.711%	$104.4498	$104.45	$104.45	$104.40
Purchase #4	$42.41	6.482%	$45.159	$45.16	$45.15	$45.20
Purchase #5	$59.87	6.223%	$63.5957	$63.60	$63.60	$63.60
Purchase #6	$18.77	8.530%	$20.3711	$20.37	$20.35	$20.40
Purchase #7	$97.83	3.759%	$101.5074	$101.51	$101.50	$101.50
7 purchase totals =	$695.27		$739.2259	$739.23	$739.20	$739.20