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	$207.56	9.484%	$227.245	$227.25	$227.25	$227.20
Purchase #2	$49.66	9.535%	$54.3951	$54.40	$54.40	$54.40
Purchase #3	$86.86	3.338%	$89.7594	$89.76	$89.75	$89.80
Purchase #4	$246.95	10.802%	$273.6255	$273.63	$273.65	$273.60
Purchase #5	$32.89	4.733%	$34.4467	$34.45	$34.45	$34.40
Purchase #6	$222.92	12.810%	$251.4761	$251.48	$251.50	$251.50
Purchase #7	$158.30	8.552%	$171.8378	$171.84	$171.85	$171.80
7 purchase totals =	$1,005.14		$1,102.7856	$1,102.81	$1,102.85	$1,102.70