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	$38.52	7.586%	$41.4421	$41.44	$41.45	$41.40
Purchase #2	$14.34	6.756%	$15.3088	$15.31	$15.30	$15.30
Purchase #3	$59.48	4.198%	$61.977	$61.98	$62.00	$62.00
Purchase #4	$134.47	4.214%	$140.1366	$140.14	$140.15	$140.10
Purchase #5	$174.37	6.756%	$186.1504	$186.15	$186.15	$186.20
Purchase #6	$176.54	5.690%	$186.5851	$186.59	$186.60	$186.60
Purchase #7	$39.29	3.168%	$40.5347	$40.53	$40.55	$40.50
7 purchase totals =	$637.01		$672.1347	$672.14	$672.20	$672.10