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	$124.27	10.375%	$137.163	$137.16	$137.15	$137.20
Purchase #2	$159.63	8.789%	$173.6599	$173.66	$173.65	$173.70
Purchase #3	$45.52	9.351%	$49.7766	$49.78	$49.80	$49.80
Purchase #4	$114.25	3.599%	$118.3619	$118.36	$118.35	$118.40
Purchase #5	$95.85	13.601%	$108.8866	$108.89	$108.90	$108.90
Purchase #6	$230.25	12.446%	$258.9069	$258.91	$258.90	$258.90
Purchase #7	$195.77	13.686%	$222.5631	$222.56	$222.55	$222.60
7 purchase totals =	$965.54		$1,069.3180	$1,069.32	$1,069.30	$1,069.50