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	$98.76	13.327%	$111.9217	$111.92	$111.90	$111.90
Purchase #2	$78.34	11.699%	$87.505	$87.51	$87.50	$87.50
Purchase #3	$176.30	3.203%	$181.9469	$181.95	$181.95	$181.90
Purchase #4	$63.53	5.542%	$67.0508	$67.05	$67.05	$67.10
Purchase #5	$86.46	5.158%	$90.9196	$90.92	$90.90	$90.90
Purchase #6	$97.50	11.316%	$108.5331	$108.53	$108.55	$108.50
Purchase #7	$105.77	5.297%	$111.3726	$111.37	$111.35	$111.40
7 purchase totals =	$706.66		$759.2497	$759.25	$759.20	$759.20