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	$100.83	10.544%	$111.4615	$111.46	$111.45	$111.50
Purchase #2	$175.52	11.730%	$196.1085	$196.11	$196.10	$196.10
Purchase #3	$68.77	8.376%	$74.5302	$74.53	$74.55	$74.50
Purchase #4	$241.42	4.276%	$251.7431	$251.74	$251.75	$251.70
Purchase #5	$162.55	13.744%	$184.8909	$184.89	$184.90	$184.90
Purchase #6	$166.82	7.522%	$179.3682	$179.37	$179.35	$179.40
Purchase #7	$15.91	9.260%	$17.3833	$17.38	$17.40	$17.40
7 purchase totals =	$931.82		$1,015.4857	$1,015.48	$1,015.50	$1,015.50