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	$41.56	7.229%	$44.5644	$44.56	$44.55	$44.60
Purchase #2	$208.61	12.244%	$234.1522	$234.15	$234.15	$234.20
Purchase #3	$116.93	8.662%	$127.0585	$127.06	$127.05	$127.10
Purchase #4	$58.83	13.250%	$66.625	$66.63	$66.65	$66.60
Purchase #5	$86.89	10.203%	$95.7554	$95.76	$95.75	$95.80
Purchase #6	$250.25	13.780%	$284.7345	$284.73	$284.75	$284.70
Purchase #7	$221.52	11.470%	$246.9283	$246.93	$246.95	$246.90
7 purchase totals =	$984.59		$1,099.8183	$1,099.82	$1,099.85	$1,099.90