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	$107.27	5.151%	$112.7955	$112.80	$112.80	$112.80
Purchase #2	$90.51	3.332%	$93.5258	$93.53	$93.55	$93.50
Purchase #3	$25.92	10.554%	$28.6556	$28.66	$28.65	$28.70
Purchase #4	$9.84	4.428%	$10.2757	$10.28	$10.30	$10.30
Purchase #5	$94.84	6.319%	$100.8329	$100.83	$100.85	$100.80
Purchase #6	$148.71	4.841%	$155.9091	$155.91	$155.90	$155.90
Purchase #7	$196.73	10.772%	$217.9218	$217.92	$217.90	$217.90
7 purchase totals =	$673.82		$719.9164	$719.93	$719.95	$719.90