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	$103.76	13.225%	$117.4823	$117.48	$117.50	$117.50
Purchase #2	$111.29	13.638%	$126.4677	$126.47	$126.45	$126.50
Purchase #3	$67.40	7.672%	$72.5709	$72.57	$72.55	$72.60
Purchase #4	$220.74	13.865%	$251.3456	$251.35	$251.35	$251.30
Purchase #5	$182.38	5.429%	$192.2814	$192.28	$192.30	$192.30
Purchase #6	$222.94	11.184%	$247.8736	$247.87	$247.85	$247.90
Purchase #7	$67.54	10.309%	$74.5027	$74.50	$74.50	$74.50
7 purchase totals =	$976.05		$1,082.5242	$1,082.52	$1,082.50	$1,082.60