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	$169.39	6.328%	$180.109	$180.11	$180.10	$180.10
Purchase #2	$50.26	5.673%	$53.1112	$53.11	$53.10	$53.10
Purchase #3	$20.54	10.130%	$22.6207	$22.62	$22.60	$22.60
Purchase #4	$83.40	7.639%	$89.7709	$89.77	$89.75	$89.80
Purchase #5	$176.29	6.154%	$187.1389	$187.14	$187.15	$187.10
Purchase #6	$202.37	11.441%	$225.5232	$225.52	$225.50	$225.50
Purchase #7	$64.89	3.222%	$66.9808	$66.98	$67.00	$67.00
7 purchase totals =	$767.14		$825.2547	$825.25	$825.20	$825.20