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	$95.85	6.671%	$102.2442	$102.24	$102.25	$102.20
Purchase #2	$124.39	4.666%	$130.194	$130.19	$130.20	$130.20
Purchase #3	$33.57	12.626%	$37.8085	$37.81	$37.80	$37.80
Purchase #4	$130.86	11.742%	$146.2256	$146.23	$146.25	$146.20
Purchase #5	$233.57	9.843%	$256.5603	$256.56	$256.55	$256.60
Purchase #6	$176.71	10.267%	$194.8528	$194.85	$194.85	$194.90
Purchase #7	$29.38	7.635%	$31.6232	$31.62	$31.60	$31.60
7 purchase totals =	$824.33		$899.5086	$899.50	$899.50	$899.50