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	$34.28	10.420%	$37.852	$37.85	$37.85	$37.90
Purchase #2	$127.83	13.760%	$145.4194	$145.42	$145.40	$145.40
Purchase #3	$59.53	11.725%	$66.5099	$66.51	$66.50	$66.50
Purchase #4	$200.99	8.609%	$218.2932	$218.29	$218.30	$218.30
Purchase #5	$19.36	6.861%	$20.6883	$20.69	$20.70	$20.70
Purchase #6	$165.46	7.288%	$177.5187	$177.52	$177.50	$177.50
Purchase #7	$214.89	11.800%	$240.247	$240.25	$240.25	$240.20
7 purchase totals =	$822.34		$906.5285	$906.53	$906.50	$906.50