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	$123.87	8.522%	$134.4262	$134.43	$134.45	$134.40
Purchase #2	$29.75	8.111%	$32.163	$32.16	$32.15	$32.20
Purchase #3	$77.78	9.696%	$85.3215	$85.32	$85.30	$85.30
Purchase #4	$79.78	7.799%	$86.002	$86.00	$86.00	$86.00
Purchase #5	$31.45	13.743%	$35.7722	$35.77	$35.75	$35.80
Purchase #6	$105.96	13.388%	$120.1459	$120.15	$120.15	$120.10
Purchase #7	$206.54	12.723%	$232.8181	$232.82	$232.80	$232.80
7 purchase totals =	$655.13		$726.6489	$726.65	$726.60	$726.60