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	$114.47	7.802%	$123.4009	$123.40	$123.40	$123.40
Purchase #2	$120.61	9.251%	$131.7676	$131.77	$131.75	$131.80
Purchase #3	$111.30	11.747%	$124.3744	$124.37	$124.35	$124.40
Purchase #4	$205.32	5.589%	$216.7953	$216.80	$216.80	$216.80
Purchase #5	$43.78	13.130%	$49.5283	$49.53	$49.55	$49.50
Purchase #6	$230.28	11.264%	$256.2187	$256.22	$256.20	$256.20
Purchase #7	$117.27	11.826%	$131.1384	$131.14	$131.15	$131.10
7 purchase totals =	$943.03		$1,033.2236	$1,033.23	$1,033.20	$1,033.20