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	$64.60	4.175%	$67.2971	$67.30	$67.30	$67.30
Purchase #2	$85.93	5.706%	$90.8332	$90.83	$90.85	$90.80
Purchase #3	$31.38	5.357%	$33.061	$33.06	$33.05	$33.10
Purchase #4	$93.85	3.694%	$97.3168	$97.32	$97.30	$97.30
Purchase #5	$55.69	6.163%	$59.1222	$59.12	$59.10	$59.10
Purchase #6	$17.69	9.486%	$19.3681	$19.37	$19.35	$19.40
Purchase #7	$63.45	13.200%	$71.8254	$71.83	$71.85	$71.80
7 purchase totals =	$412.59		$438.8238	$438.83	$438.80	$438.80