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	$211.51	12.234%	$237.3861	$237.39	$237.40	$237.40
Purchase #2	$146.68	10.770%	$162.4774	$162.48	$162.50	$162.50
Purchase #3	$132.49	13.793%	$150.7643	$150.76	$150.75	$150.80
Purchase #4	$177.39	7.532%	$190.751	$190.75	$190.75	$190.80
Purchase #5	$58.36	5.503%	$61.5716	$61.57	$61.55	$61.60
Purchase #6	$111.45	4.488%	$116.4519	$116.45	$116.45	$116.50
Purchase #7	$40.31	3.247%	$41.6189	$41.62	$41.60	$41.60
7 purchase totals =	$878.19		$961.0212	$961.02	$961.00	$961.20