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	$148.34	10.691%	$164.199	$164.20	$164.20	$164.20
Purchase #2	$127.35	13.385%	$144.3958	$144.40	$144.40	$144.40
Purchase #3	$90.32	5.386%	$95.1846	$95.18	$95.20	$95.20
Purchase #4	$238.40	8.369%	$258.3517	$258.35	$258.35	$258.40
Purchase #5	$40.39	7.628%	$43.4709	$43.47	$43.45	$43.50
Purchase #6	$109.55	13.515%	$124.3557	$124.36	$124.35	$124.40
Purchase #7	$232.77	3.570%	$241.0799	$241.08	$241.10	$241.10
7 purchase totals =	$987.12		$1,071.0376	$1,071.04	$1,071.05	$1,071.20