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	$21.73	3.246%	$22.4354	$22.44	$22.45	$22.40
Purchase #2	$242.45	5.479%	$255.7338	$255.73	$255.75	$255.70
Purchase #3	$82.63	11.788%	$92.3704	$92.37	$92.35	$92.40
Purchase #4	$42.40	6.558%	$45.1806	$45.18	$45.20	$45.20
Purchase #5	$207.44	5.680%	$219.2226	$219.22	$219.20	$219.20
Purchase #6	$202.92	11.247%	$225.7424	$225.74	$225.75	$225.70
Purchase #7	$176.84	4.698%	$185.1479	$185.15	$185.15	$185.10
7 purchase totals =	$976.41		$1,045.8331	$1,045.83	$1,045.85	$1,045.70