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	$126.72	4.412%	$132.3109	$132.31	$132.30	$132.30
Purchase #2	$218.72	4.167%	$227.8341	$227.83	$227.85	$227.80
Purchase #3	$237.88	7.104%	$254.779	$254.78	$254.80	$254.80
Purchase #4	$73.27	4.649%	$76.6763	$76.68	$76.70	$76.70
Purchase #5	$211.64	6.249%	$224.8654	$224.87	$224.85	$224.90
Purchase #6	$141.90	11.436%	$158.1277	$158.13	$158.15	$158.10
Purchase #7	$113.59	7.613%	$122.2376	$122.24	$122.25	$122.20
7 purchase totals =	$1,123.72		$1,196.8310	$1,196.84	$1,196.90	$1,196.80