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	$63.72	3.505%	$65.9534	$65.95	$65.95	$66.00
Purchase #2	$75.80	10.205%	$83.5354	$83.54	$83.55	$83.50
Purchase #3	$150.87	4.746%	$158.0303	$158.03	$158.05	$158.00
Purchase #4	$115.31	9.417%	$126.1687	$126.17	$126.15	$126.20
Purchase #5	$160.77	13.140%	$181.8952	$181.90	$181.90	$181.90
Purchase #6	$92.42	5.543%	$97.5428	$97.54	$97.55	$97.50
Purchase #7	$78.34	12.223%	$87.9155	$87.92	$87.90	$87.90
7 purchase totals =	$737.23		$801.0413	$801.05	$801.05	$801.00