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	$47.97	11.582%	$53.5259	$53.53	$53.55	$53.50
Purchase #2	$96.94	10.598%	$107.2137	$107.21	$107.20	$107.20
Purchase #3	$82.52	11.643%	$92.1278	$92.13	$92.15	$92.10
Purchase #4	$18.45	8.496%	$20.0175	$20.02	$20.00	$20.00
Purchase #5	$37.28	3.360%	$38.5326	$38.53	$38.55	$38.50
Purchase #6	$63.55	13.431%	$72.0854	$72.09	$72.10	$72.10
Purchase #7	$215.33	4.635%	$225.3105	$225.31	$225.30	$225.30
7 purchase totals =	$562.04		$608.8134	$608.82	$608.85	$608.70