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	$88.76	7.430%	$95.3549	$95.35	$95.35	$95.40
Purchase #2	$109.75	6.450%	$116.8289	$116.83	$116.85	$116.80
Purchase #3	$214.61	8.780%	$233.4528	$233.45	$233.45	$233.50
Purchase #4	$250.62	6.724%	$267.4717	$267.47	$267.45	$267.50
Purchase #5	$50.83	8.556%	$55.179	$55.18	$55.20	$55.20
Purchase #6	$38.76	5.625%	$40.9403	$40.94	$40.95	$40.90
Purchase #7	$182.96	5.143%	$192.3696	$192.37	$192.35	$192.40
7 purchase totals =	$936.29		$1,001.5972	$1,001.59	$1,001.60	$1,001.70