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	$87.25	12.166%	$97.8648	$97.86	$97.85	$97.90
Purchase #2	$140.46	3.321%	$145.1247	$145.12	$145.10	$145.10
Purchase #3	$37.35	9.213%	$40.7911	$40.79	$40.80	$40.80
Purchase #4	$234.41	10.443%	$258.8894	$258.89	$258.90	$258.90
Purchase #5	$193.47	12.384%	$217.4293	$217.43	$217.45	$217.40
Purchase #6	$62.27	5.117%	$65.4564	$65.46	$65.45	$65.50
Purchase #7	$232.26	3.708%	$240.8722	$240.87	$240.85	$240.90
7 purchase totals =	$987.47		$1,066.4279	$1,066.42	$1,066.40	$1,066.50