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	$160.48	7.295%	$172.187	$172.19	$172.20	$172.20
Purchase #2	$220.32	5.827%	$233.158	$233.16	$233.15	$233.20
Purchase #3	$196.42	10.786%	$217.6059	$217.61	$217.60	$217.60
Purchase #4	$73.72	12.476%	$82.9173	$82.92	$82.90	$82.90
Purchase #5	$41.67	8.505%	$45.214	$45.21	$45.20	$45.20
Purchase #6	$198.43	4.476%	$207.3117	$207.31	$207.30	$207.30
Purchase #7	$98.55	12.124%	$110.4982	$110.50	$110.50	$110.50
7 purchase totals =	$989.59		$1,068.8921	$1,068.90	$1,068.85	$1,068.90