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	$32.45	3.748%	$33.6662	$33.67	$33.65	$33.70
Purchase #2	$76.74	4.193%	$79.9577	$79.96	$79.95	$80.00
Purchase #3	$218.74	6.521%	$233.004	$233.00	$233.00	$233.00
Purchase #4	$17.89	4.329%	$18.6645	$18.66	$18.65	$18.70
Purchase #5	$143.48	6.850%	$153.3084	$153.31	$153.30	$153.30
Purchase #6	$6.69	6.593%	$7.1311	$7.13	$7.15	$7.10
Purchase #7	$95.55	9.761%	$104.8766	$104.88	$104.90	$104.90
7 purchase totals =	$591.54		$630.6085	$630.61	$630.60	$630.70