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	$103.56	4.856%	$108.5889	$108.59	$108.60	$108.60
Purchase #2	$167.94	9.583%	$184.0337	$184.03	$184.05	$184.00
Purchase #3	$72.90	5.502%	$76.911	$76.91	$76.90	$76.90
Purchase #4	$80.69	11.122%	$89.6643	$89.66	$89.65	$89.70
Purchase #5	$105.80	13.330%	$119.9031	$119.90	$119.90	$119.90
Purchase #6	$86.27	7.675%	$92.8912	$92.89	$92.90	$92.90
Purchase #7	$21.83	13.407%	$24.7567	$24.76	$24.75	$24.80
7 purchase totals =	$638.99		$696.7489	$696.74	$696.75	$696.80