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	$72.85	6.651%	$77.6953	$77.70	$77.70	$77.70
Purchase #2	$139.83	9.651%	$153.325	$153.33	$153.35	$153.30
Purchase #3	$227.76	5.866%	$241.1204	$241.12	$241.10	$241.10
Purchase #4	$64.83	11.673%	$72.3976	$72.40	$72.40	$72.40
Purchase #5	$60.82	11.772%	$67.9797	$67.98	$68.00	$68.00
Purchase #6	$33.51	7.242%	$35.9368	$35.94	$35.95	$35.90
Purchase #7	$69.45	10.667%	$76.8582	$76.86	$76.85	$76.90
7 purchase totals =	$669.05		$725.3130	$725.33	$725.35	$725.30