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	$92.25	8.805%	$100.3726	$100.37	$100.35	$100.40
Purchase #2	$156.71	3.772%	$162.6211	$162.62	$162.60	$162.60
Purchase #3	$14.38	10.219%	$15.8495	$15.85	$15.85	$15.80
Purchase #4	$82.32	13.737%	$93.6283	$93.63	$93.65	$93.60
Purchase #5	$24.29	7.627%	$26.1426	$26.14	$26.15	$26.10
Purchase #6	$85.99	3.857%	$89.3066	$89.31	$89.30	$89.30
Purchase #7	$130.85	6.693%	$139.6078	$139.61	$139.60	$139.60
7 purchase totals =	$586.79		$627.5285	$627.53	$627.50	$627.40