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	$189.85	12.275%	$213.1541	$213.15	$213.15	$213.20
Purchase #2	$103.66	4.666%	$108.4968	$108.50	$108.50	$108.50
Purchase #3	$43.27	13.869%	$49.2711	$49.27	$49.25	$49.30
Purchase #4	$33.56	6.850%	$35.8589	$35.86	$35.85	$35.90
Purchase #5	$178.77	5.659%	$188.8866	$188.89	$188.90	$188.90
Purchase #6	$160.38	7.668%	$172.6779	$172.68	$172.70	$172.70
Purchase #7	$95.59	3.818%	$99.2396	$99.24	$99.25	$99.20
7 purchase totals =	$805.08		$867.5850	$867.59	$867.60	$867.70