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	$172.34	11.439%	$192.054	$192.05	$192.05	$192.10
Purchase #2	$101.97	7.601%	$109.7207	$109.72	$109.70	$109.70
Purchase #3	$132.84	10.743%	$147.111	$147.11	$147.10	$147.10
Purchase #4	$143.69	11.688%	$160.4845	$160.48	$160.50	$160.50
Purchase #5	$108.82	10.848%	$120.6248	$120.62	$120.60	$120.60
Purchase #6	$184.85	13.509%	$209.8214	$209.82	$209.80	$209.80
Purchase #7	$49.50	9.307%	$54.107	$54.11	$54.10	$54.10
7 purchase totals =	$894.01		$993.9234	$993.91	$993.85	$993.90