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	$148.60	5.231%	$156.3733	$156.37	$156.35	$156.40
Purchase #2	$46.52	8.724%	$50.5784	$50.58	$50.60	$50.60
Purchase #3	$115.61	10.155%	$127.3502	$127.35	$127.35	$127.40
Purchase #4	$36.66	5.119%	$38.5366	$38.54	$38.55	$38.50
Purchase #5	$192.64	3.366%	$199.1243	$199.12	$199.10	$199.10
Purchase #6	$113.64	3.598%	$117.7288	$117.73	$117.75	$117.70
Purchase #7	$165.31	8.156%	$178.7927	$178.79	$178.80	$178.80
7 purchase totals =	$818.98		$868.4843	$868.48	$868.50	$868.50