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	$152.34	13.290%	$172.586	$172.59	$172.60	$172.60
Purchase #2	$145.78	13.466%	$165.4107	$165.41	$165.40	$165.40
Purchase #3	$130.29	8.465%	$141.319	$141.32	$141.30	$141.30
Purchase #4	$68.85	10.533%	$76.102	$76.10	$76.10	$76.10
Purchase #5	$224.53	13.495%	$254.8303	$254.83	$254.85	$254.80
Purchase #6	$38.89	6.841%	$41.5505	$41.55	$41.55	$41.60
Purchase #7	$13.37	13.394%	$15.1608	$15.16	$15.15	$15.20
7 purchase totals =	$774.05		$866.9593	$866.96	$866.95	$867.00