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	$218.92	11.529%	$244.1593	$244.16	$244.15	$244.20
Purchase #2	$15.27	6.583%	$16.2752	$16.28	$16.30	$16.30
Purchase #3	$103.43	7.412%	$111.0962	$111.10	$111.10	$111.10
Purchase #4	$113.71	4.324%	$118.6268	$118.63	$118.65	$118.60
Purchase #5	$86.55	4.139%	$90.1323	$90.13	$90.15	$90.10
Purchase #6	$35.60	4.151%	$37.0778	$37.08	$37.10	$37.10
Purchase #7	$225.58	3.666%	$233.8498	$233.85	$233.85	$233.80
7 purchase totals =	$799.06		$851.2174	$851.23	$851.30	$851.20