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	$116.90	11.779%	$130.6697	$130.67	$130.65	$130.70
Purchase #2	$161.35	4.313%	$168.309	$168.31	$168.30	$168.30
Purchase #3	$101.81	9.782%	$111.7691	$111.77	$111.75	$111.80
Purchase #4	$56.51	5.830%	$59.8045	$59.80	$59.80	$59.80
Purchase #5	$217.50	9.185%	$237.4774	$237.48	$237.50	$237.50
Purchase #6	$65.78	13.791%	$74.8517	$74.85	$74.85	$74.90
Purchase #7	$78.38	3.805%	$81.3624	$81.36	$81.35	$81.40
7 purchase totals =	$798.23		$864.2438	$864.24	$864.20	$864.40