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	$208.96	8.319%	$226.3434	$226.34	$226.35	$226.30
Purchase #2	$56.68	10.124%	$62.4183	$62.42	$62.40	$62.40
Purchase #3	$194.35	3.151%	$200.474	$200.47	$200.45	$200.50
Purchase #4	$186.62	9.564%	$204.4683	$204.47	$204.45	$204.50
Purchase #5	$67.41	5.667%	$71.2301	$71.23	$71.25	$71.20
Purchase #6	$49.40	13.790%	$56.2123	$56.21	$56.20	$56.20
Purchase #7	$95.47	4.128%	$99.411	$99.41	$99.40	$99.40
7 purchase totals =	$858.89		$920.5574	$920.55	$920.50	$920.50