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	$194.42	12.599%	$218.915	$218.92	$218.90	$218.90
Purchase #2	$148.55	5.431%	$156.6178	$156.62	$156.60	$156.60
Purchase #3	$13.72	12.712%	$15.4641	$15.46	$15.45	$15.50
Purchase #4	$193.25	8.276%	$209.2434	$209.24	$209.25	$209.20
Purchase #5	$68.27	4.450%	$71.308	$71.31	$71.30	$71.30
Purchase #6	$161.45	9.190%	$176.2873	$176.29	$176.30	$176.30
Purchase #7	$195.47	9.502%	$214.0436	$214.04	$214.05	$214.00
7 purchase totals =	$975.13		$1,061.8792	$1,061.88	$1,061.85	$1,061.80