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	$107.54	10.572%	$118.9091	$118.91	$118.90	$118.90
Purchase #2	$36.47	5.243%	$38.3821	$38.38	$38.40	$38.40
Purchase #3	$56.43	12.198%	$63.3133	$63.31	$63.30	$63.30
Purchase #4	$206.74	4.858%	$216.7834	$216.78	$216.80	$216.80
Purchase #5	$227.52	12.308%	$255.5232	$255.52	$255.50	$255.50
Purchase #6	$93.37	12.568%	$105.1047	$105.10	$105.10	$105.10
Purchase #7	$138.28	8.317%	$149.7807	$149.78	$149.80	$149.80
7 purchase totals =	$866.35		$947.7965	$947.78	$947.80	$947.80