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	$49.34	7.808%	$53.1925	$53.19	$53.20	$53.20
Purchase #2	$63.60	6.281%	$67.5947	$67.59	$67.60	$67.60
Purchase #3	$51.66	6.214%	$54.8702	$54.87	$54.85	$54.90
Purchase #4	$74.83	13.596%	$85.0039	$85.00	$85.00	$85.00
Purchase #5	$147.37	5.571%	$155.58	$155.58	$155.60	$155.60
Purchase #6	$54.54	3.310%	$56.3453	$56.35	$56.35	$56.30
Purchase #7	$230.90	6.794%	$246.5873	$246.59	$246.60	$246.60
7 purchase totals =	$672.24		$719.1739	$719.17	$719.20	$719.20