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	$50.33	7.367%	$54.0378	$54.04	$54.05	$54.00
Purchase #2	$130.35	10.664%	$144.2505	$144.25	$144.25	$144.30
Purchase #3	$96.30	12.249%	$108.0958	$108.10	$108.10	$108.10
Purchase #4	$156.77	10.284%	$172.8922	$172.89	$172.90	$172.90
Purchase #5	$68.59	3.114%	$70.7259	$70.73	$70.75	$70.70
Purchase #6	$187.49	12.525%	$210.9731	$210.97	$210.95	$211.00
Purchase #7	$175.82	8.204%	$190.2443	$190.24	$190.25	$190.20
7 purchase totals =	$865.65		$951.2196	$951.22	$951.25	$951.20