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	$197.92	10.573%	$218.8461	$218.85	$218.85	$218.80
Purchase #2	$93.43	10.246%	$103.0028	$103.00	$103.00	$103.00
Purchase #3	$108.41	7.214%	$116.2307	$116.23	$116.25	$116.20
Purchase #4	$133.82	13.845%	$152.3474	$152.35	$152.35	$152.30
Purchase #5	$133.43	4.581%	$139.5424	$139.54	$139.55	$139.50
Purchase #6	$166.37	5.383%	$175.3257	$175.33	$175.35	$175.30
Purchase #7	$33.43	6.471%	$35.5933	$35.59	$35.60	$35.60
7 purchase totals =	$866.81		$940.8884	$940.89	$940.95	$940.70