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	$145.50	5.197%	$153.0616	$153.06	$153.05	$153.10
Purchase #2	$222.66	10.675%	$246.429	$246.43	$246.45	$246.40
Purchase #3	$57.53	4.578%	$60.1637	$60.16	$60.15	$60.20
Purchase #4	$16.55	6.604%	$17.643	$17.64	$17.65	$17.60
Purchase #5	$176.41	11.123%	$196.0321	$196.03	$196.05	$196.00
Purchase #6	$212.96	12.447%	$239.4671	$239.47	$239.45	$239.50
Purchase #7	$93.64	11.209%	$104.1361	$104.14	$104.15	$104.10
7 purchase totals =	$925.25		$1,016.9326	$1,016.93	$1,016.95	$1,016.90