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	$47.48	4.440%	$49.5881	$49.59	$49.60	$49.60
Purchase #2	$86.30	8.189%	$93.3671	$93.37	$93.35	$93.40
Purchase #3	$98.82	12.674%	$111.3444	$111.34	$111.35	$111.30
Purchase #4	$54.81	7.191%	$58.7514	$58.75	$58.75	$58.80
Purchase #5	$91.82	4.232%	$95.7058	$95.71	$95.70	$95.70
Purchase #6	$65.36	3.144%	$67.4149	$67.41	$67.40	$67.40
Purchase #7	$21.93	11.357%	$24.4206	$24.42	$24.40	$24.40
7 purchase totals =	$466.52		$500.5923	$500.59	$500.55	$500.60