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	$154.29	9.698%	$169.253	$169.25	$169.25	$169.30
Purchase #2	$32.85	5.323%	$34.5986	$34.60	$34.60	$34.60
Purchase #3	$133.91	6.209%	$142.2245	$142.22	$142.20	$142.20
Purchase #4	$171.37	8.149%	$185.3349	$185.33	$185.35	$185.30
Purchase #5	$24.40	11.119%	$27.113	$27.11	$27.10	$27.10
Purchase #6	$237.73	4.266%	$247.8716	$247.87	$247.85	$247.90
Purchase #7	$95.51	10.617%	$105.6503	$105.65	$105.65	$105.70
7 purchase totals =	$850.06		$912.0459	$912.03	$912.00	$912.10