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	$86.77	7.454%	$93.2378	$93.24	$93.25	$93.20
Purchase #2	$91.85	9.671%	$100.7328	$100.73	$100.75	$100.70
Purchase #3	$31.87	11.651%	$35.5832	$35.58	$35.60	$35.60
Purchase #4	$57.37	7.114%	$61.4513	$61.45	$61.45	$61.50
Purchase #5	$104.30	6.805%	$111.3976	$111.40	$111.40	$111.40
Purchase #6	$90.92	10.269%	$100.2566	$100.26	$100.25	$100.30
Purchase #7	$34.25	13.615%	$38.9131	$38.91	$38.90	$38.90
7 purchase totals =	$497.33		$541.5724	$541.57	$541.60	$541.60