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	$151.83	5.443%	$160.0941	$160.09	$160.10	$160.10
Purchase #2	$179.26	6.320%	$190.5892	$190.59	$190.60	$190.60
Purchase #3	$125.82	13.470%	$142.768	$142.77	$142.75	$142.80
Purchase #4	$64.49	4.118%	$67.1457	$67.15	$67.15	$67.10
Purchase #5	$219.90	9.679%	$241.1841	$241.18	$241.20	$241.20
Purchase #6	$52.58	10.842%	$58.2807	$58.28	$58.30	$58.30
Purchase #7	$196.32	6.462%	$209.0062	$209.01	$209.00	$209.00
7 purchase totals =	$990.20		$1,069.0680	$1,069.07	$1,069.10	$1,069.10