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	$159.84	8.607%	$173.5974	$173.60	$173.60	$173.60
Purchase #2	$207.50	10.325%	$228.9244	$228.92	$228.90	$228.90
Purchase #3	$37.77	4.829%	$39.5939	$39.59	$39.60	$39.60
Purchase #4	$161.59	4.261%	$168.4753	$168.48	$168.50	$168.50
Purchase #5	$153.84	11.347%	$171.2962	$171.30	$171.30	$171.30
Purchase #6	$11.58	3.487%	$11.9838	$11.98	$12.00	$12.00
Purchase #7	$226.86	4.295%	$236.6036	$236.60	$236.60	$236.60
7 purchase totals =	$958.98		$1,030.4746	$1,030.47	$1,030.50	$1,030.50