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	$184.84	3.532%	$191.3685	$191.37	$191.35	$191.40
Purchase #2	$10.91	4.365%	$11.3862	$11.39	$11.40	$11.40
Purchase #3	$201.69	9.680%	$221.2136	$221.21	$221.20	$221.20
Purchase #4	$207.35	7.437%	$222.7706	$222.77	$222.75	$222.80
Purchase #5	$154.82	11.117%	$172.0313	$172.03	$172.05	$172.00
Purchase #6	$169.71	12.262%	$190.5198	$190.52	$190.50	$190.50
Purchase #7	$27.72	5.813%	$29.3314	$29.33	$29.35	$29.30
7 purchase totals =	$957.04		$1,038.6214	$1,038.62	$1,038.60	$1,038.60