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	$80.29	11.502%	$89.525	$89.53	$89.55	$89.50
Purchase #2	$227.27	10.269%	$250.6084	$250.61	$250.60	$250.60
Purchase #3	$69.82	10.308%	$77.017	$77.02	$77.00	$77.00
Purchase #4	$234.31	5.504%	$247.2064	$247.21	$247.20	$247.20
Purchase #5	$222.86	4.227%	$232.2803	$232.28	$232.30	$232.30
Purchase #6	$241.89	8.823%	$263.232	$263.23	$263.25	$263.20
Purchase #7	$56.26	11.246%	$62.587	$62.59	$62.60	$62.60
7 purchase totals =	$1,132.70		$1,222.4561	$1,222.47	$1,222.50	$1,222.40