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	$34.29	5.316%	$36.1129	$36.11	$36.10	$36.10
Purchase #2	$84.39	8.837%	$91.8475	$91.85	$91.85	$91.80
Purchase #3	$113.30	12.527%	$127.4931	$127.49	$127.50	$127.50
Purchase #4	$233.34	7.868%	$251.6992	$251.70	$251.70	$251.70
Purchase #5	$101.51	6.488%	$108.096	$108.10	$108.10	$108.10
Purchase #6	$157.59	4.192%	$164.1962	$164.20	$164.20	$164.20
Purchase #7	$104.45	6.614%	$111.3583	$111.36	$111.35	$111.40
7 purchase totals =	$828.87		$890.8032	$890.81	$890.80	$890.80