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	$187.94	11.834%	$210.1808	$210.18	$210.20	$210.20
Purchase #2	$153.43	4.584%	$160.4632	$160.46	$160.45	$160.50
Purchase #3	$27.29	5.135%	$28.6913	$28.69	$28.70	$28.70
Purchase #4	$151.79	3.307%	$156.8097	$156.81	$156.80	$156.80
Purchase #5	$101.80	3.671%	$105.5371	$105.54	$105.55	$105.50
Purchase #6	$199.68	7.410%	$214.4763	$214.48	$214.50	$214.50
Purchase #7	$213.95	4.545%	$223.674	$223.67	$223.65	$223.70
7 purchase totals =	$1,035.88		$1,099.8324	$1,099.83	$1,099.85	$1,099.90