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	$64.97	3.484%	$67.2336	$67.23	$67.25	$67.20
Purchase #2	$99.59	10.371%	$109.9185	$109.92	$109.90	$109.90
Purchase #3	$153.71	11.683%	$171.6679	$171.67	$171.65	$171.70
Purchase #4	$21.77	4.844%	$22.8245	$22.82	$22.80	$22.80
Purchase #5	$146.57	8.569%	$159.1296	$159.13	$159.15	$159.10
Purchase #6	$101.70	11.539%	$113.4352	$113.44	$113.45	$113.40
Purchase #7	$200.98	13.370%	$227.851	$227.85	$227.85	$227.90
7 purchase totals =	$789.29		$872.0603	$872.06	$872.05	$872.00