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	$133.31	13.191%	$150.8949	$150.89	$150.90	$150.90
Purchase #2	$154.45	12.282%	$173.4195	$173.42	$173.40	$173.40
Purchase #3	$159.45	13.722%	$181.3297	$181.33	$181.35	$181.30
Purchase #4	$57.51	10.572%	$63.59	$63.59	$63.60	$63.60
Purchase #5	$92.89	4.571%	$97.136	$97.14	$97.15	$97.10
Purchase #6	$225.55	7.766%	$243.0662	$243.07	$243.05	$243.10
Purchase #7	$15.76	10.610%	$17.4321	$17.43	$17.45	$17.40
7 purchase totals =	$838.92		$926.8684	$926.87	$926.90	$926.80