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	$122.89	3.766%	$127.518	$127.52	$127.50	$127.50
Purchase #2	$96.73	6.308%	$102.8317	$102.83	$102.85	$102.80
Purchase #3	$96.64	13.864%	$110.0382	$110.04	$110.05	$110.00
Purchase #4	$84.68	6.705%	$90.3578	$90.36	$90.35	$90.40
Purchase #5	$19.59	10.650%	$21.6763	$21.68	$21.70	$21.70
Purchase #6	$49.82	11.778%	$55.6878	$55.69	$55.70	$55.70
Purchase #7	$220.74	12.244%	$247.7674	$247.77	$247.75	$247.80
7 purchase totals =	$691.09		$755.8772	$755.89	$755.90	$755.90