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	$22.59	10.441%	$24.9486	$24.95	$24.95	$24.90
Purchase #2	$93.55	5.198%	$98.4127	$98.41	$98.40	$98.40
Purchase #3	$102.88	8.634%	$111.7627	$111.76	$111.75	$111.80
Purchase #4	$19.96	6.327%	$21.2229	$21.22	$21.20	$21.20
Purchase #5	$151.25	5.353%	$159.3464	$159.35	$159.35	$159.30
Purchase #6	$240.43	13.809%	$273.631	$273.63	$273.65	$273.60
Purchase #7	$116.79	12.440%	$131.3187	$131.32	$131.30	$131.30
7 purchase totals =	$747.45		$820.6430	$820.64	$820.60	$820.50