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	$72.92	13.317%	$82.6308	$82.63	$82.65	$82.60
Purchase #2	$94.77	11.496%	$105.6648	$105.66	$105.65	$105.70
Purchase #3	$69.66	10.413%	$76.9137	$76.91	$76.90	$76.90
Purchase #4	$142.78	9.584%	$156.464	$156.46	$156.45	$156.50
Purchase #5	$163.67	4.117%	$170.4083	$170.41	$170.40	$170.40
Purchase #6	$144.29	6.469%	$153.6241	$153.62	$153.60	$153.60
Purchase #7	$47.89	7.481%	$51.4727	$51.47	$51.45	$51.50
7 purchase totals =	$735.98		$797.1784	$797.16	$797.10	$797.20