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	$43.35	5.168%	$45.5903	$45.59	$45.60	$45.60
Purchase #2	$92.36	8.202%	$99.9354	$99.94	$99.95	$99.90
Purchase #3	$181.53	11.464%	$202.3406	$202.34	$202.35	$202.30
Purchase #4	$190.26	3.450%	$196.824	$196.82	$196.80	$196.80
Purchase #5	$101.57	3.820%	$105.45	$105.45	$105.45	$105.50
Purchase #6	$24.66	6.208%	$26.1909	$26.19	$26.20	$26.20
Purchase #7	$162.28	13.169%	$183.6507	$183.65	$183.65	$183.70
7 purchase totals =	$796.01		$859.9819	$859.98	$860.00	$860.00