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	$94.57	12.528%	$106.4177	$106.42	$106.40	$106.40
Purchase #2	$176.29	5.769%	$186.4602	$186.46	$186.45	$186.50
Purchase #3	$221.75	3.139%	$228.7107	$228.71	$228.70	$228.70
Purchase #4	$155.91	13.627%	$177.1559	$177.16	$177.15	$177.20
Purchase #5	$41.38	3.435%	$42.8014	$42.80	$42.80	$42.80
Purchase #6	$83.56	8.437%	$90.61	$90.61	$90.60	$90.60
Purchase #7	$209.93	13.729%	$238.7513	$238.75	$238.75	$238.80
7 purchase totals =	$983.39		$1,070.9072	$1,070.91	$1,070.85	$1,071.00