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	$126.36	4.436%	$131.9653	$131.97	$131.95	$132.00
Purchase #2	$101.59	5.546%	$107.2242	$107.22	$107.20	$107.20
Purchase #3	$14.59	11.294%	$16.2378	$16.24	$16.25	$16.20
Purchase #4	$100.78	10.365%	$111.2258	$111.23	$111.25	$111.20
Purchase #5	$137.59	10.406%	$151.9076	$151.91	$151.90	$151.90
Purchase #6	$78.95	10.209%	$87.01	$87.01	$87.00	$87.00
Purchase #7	$172.38	7.489%	$185.2895	$185.29	$185.30	$185.30
7 purchase totals =	$732.24		$790.8602	$790.87	$790.85	$790.80