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	$108.30	3.576%	$112.1728	$112.17	$112.15	$112.20
Purchase #2	$66.52	11.140%	$73.9303	$73.93	$73.95	$73.90
Purchase #3	$146.37	7.312%	$157.0726	$157.07	$157.05	$157.10
Purchase #4	$230.49	3.616%	$238.8245	$238.82	$238.80	$238.80
Purchase #5	$85.33	5.410%	$89.9464	$89.95	$89.95	$89.90
Purchase #6	$160.87	4.754%	$168.5178	$168.52	$168.50	$168.50
Purchase #7	$63.40	5.308%	$66.7653	$66.77	$66.75	$66.80
7 purchase totals =	$861.28		$907.2297	$907.23	$907.15	$907.20