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	$167.98	3.356%	$173.6174	$173.62	$173.60	$173.60
Purchase #2	$65.76	8.719%	$71.4936	$71.49	$71.50	$71.50
Purchase #3	$134.58	3.782%	$139.6698	$139.67	$139.65	$139.70
Purchase #4	$87.30	3.371%	$90.2429	$90.24	$90.25	$90.20
Purchase #5	$150.54	7.784%	$162.258	$162.26	$162.25	$162.30
Purchase #6	$63.99	6.392%	$68.0802	$68.08	$68.10	$68.10
Purchase #7	$150.39	11.722%	$168.0187	$168.02	$168.00	$168.00
7 purchase totals =	$820.54		$873.3806	$873.38	$873.35	$873.40