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	$142.61	4.460%	$148.9704	$148.97	$148.95	$149.00
Purchase #2	$75.29	9.587%	$82.5081	$82.51	$82.50	$82.50
Purchase #3	$153.98	12.618%	$173.4092	$173.41	$173.40	$173.40
Purchase #4	$106.32	3.594%	$110.1411	$110.14	$110.15	$110.10
Purchase #5	$212.64	7.171%	$227.8884	$227.89	$227.90	$227.90
Purchase #6	$11.39	7.834%	$12.2823	$12.28	$12.30	$12.30
Purchase #7	$118.93	3.747%	$123.3863	$123.39	$123.40	$123.40
7 purchase totals =	$821.16		$878.5858	$878.59	$878.60	$878.60