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	$26.69	9.732%	$29.2875	$29.29	$29.30	$29.30
Purchase #2	$35.48	9.593%	$38.8836	$38.88	$38.90	$38.90
Purchase #3	$176.88	4.721%	$185.2305	$185.23	$185.25	$185.20
Purchase #4	$9.80	9.356%	$10.7169	$10.72	$10.70	$10.70
Purchase #5	$9.35	8.461%	$10.1411	$10.14	$10.15	$10.10
Purchase #6	$35.54	5.608%	$37.5331	$37.53	$37.55	$37.50
Purchase #7	$69.78	9.766%	$76.5947	$76.59	$76.60	$76.60
7 purchase totals =	$363.52		$388.3874	$388.38	$388.45	$388.30