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	$55.81	6.230%	$59.287	$59.29	$59.30	$59.30
Purchase #2	$21.65	12.582%	$24.374	$24.37	$24.35	$24.40
Purchase #3	$92.99	10.871%	$103.0989	$103.10	$103.10	$103.10
Purchase #4	$138.29	11.182%	$153.7536	$153.75	$153.75	$153.80
Purchase #5	$97.66	12.233%	$109.6067	$109.61	$109.60	$109.60
Purchase #6	$14.75	11.319%	$16.4196	$16.42	$16.40	$16.40
Purchase #7	$139.60	11.222%	$155.2659	$155.27	$155.25	$155.30
7 purchase totals =	$560.75		$621.8057	$621.81	$621.75	$621.90