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	$172.65	11.393%	$192.32	$192.32	$192.30	$192.30
Purchase #2	$19.61	11.259%	$21.8179	$21.82	$21.80	$21.80
Purchase #3	$5.67	3.485%	$5.8676	$5.87	$5.85	$5.90
Purchase #4	$219.56	6.358%	$233.5196	$233.52	$233.50	$233.50
Purchase #5	$143.56	5.696%	$151.7372	$151.74	$151.75	$151.70
Purchase #6	$250.92	11.307%	$279.2915	$279.29	$279.30	$279.30
Purchase #7	$80.75	7.231%	$86.589	$86.59	$86.60	$86.60
7 purchase totals =	$892.72		$971.1428	$971.15	$971.10	$971.10