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	$144.46	12.514%	$162.5377	$162.54	$162.55	$162.50
Purchase #2	$106.97	5.162%	$112.4918	$112.49	$112.50	$112.50
Purchase #3	$132.64	13.206%	$150.1564	$150.16	$150.15	$150.20
Purchase #4	$152.55	13.203%	$172.6912	$172.69	$172.70	$172.70
Purchase #5	$7.81	12.392%	$8.7778	$8.78	$8.80	$8.80
Purchase #6	$234.29	12.209%	$262.8945	$262.89	$262.90	$262.90
Purchase #7	$118.85	4.415%	$124.0972	$124.10	$124.10	$124.10
7 purchase totals =	$897.57		$993.6466	$993.65	$993.70	$993.70