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	$130.64	9.174%	$142.6249	$142.62	$142.60	$142.60
Purchase #2	$131.54	10.450%	$145.2859	$145.29	$145.30	$145.30
Purchase #3	$62.91	12.316%	$70.658	$70.66	$70.65	$70.70
Purchase #4	$192.41	11.640%	$214.8065	$214.81	$214.80	$214.80
Purchase #5	$162.39	13.838%	$184.8615	$184.86	$184.85	$184.90
Purchase #6	$235.39	9.160%	$256.9517	$256.95	$256.95	$257.00
Purchase #7	$37.75	7.502%	$40.582	$40.58	$40.60	$40.60
7 purchase totals =	$953.03		$1,055.7705	$1,055.77	$1,055.75	$1,055.90