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	$88.89	11.166%	$98.8155	$98.82	$98.80	$98.80
Purchase #2	$93.74	10.390%	$103.4796	$103.48	$103.50	$103.50
Purchase #3	$11.69	7.575%	$12.5755	$12.58	$12.60	$12.60
Purchase #4	$228.48	10.247%	$251.8923	$251.89	$251.90	$251.90
Purchase #5	$207.76	6.776%	$221.8378	$221.84	$221.85	$221.80
Purchase #6	$25.40	8.409%	$27.5359	$27.54	$27.55	$27.50
Purchase #7	$215.94	7.370%	$231.8548	$231.85	$231.85	$231.90
7 purchase totals =	$871.90		$947.9914	$948.00	$948.05	$948.00