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	$123.87	6.600%	$132.0454	$132.05	$132.05	$132.00
Purchase #2	$17.41	8.439%	$18.8792	$18.88	$18.90	$18.90
Purchase #3	$157.61	9.217%	$172.1369	$172.14	$172.15	$172.10
Purchase #4	$150.69	5.583%	$159.103	$159.10	$159.10	$159.10
Purchase #5	$97.36	9.579%	$106.6861	$106.69	$106.70	$106.70
Purchase #6	$100.82	5.706%	$106.5728	$106.57	$106.55	$106.60
Purchase #7	$222.42	4.826%	$233.154	$233.15	$233.15	$233.20
7 purchase totals =	$870.18		$928.5774	$928.58	$928.60	$928.60