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	$92.84	7.732%	$100.0184	$100.02	$100.00	$100.00
Purchase #2	$97.51	13.843%	$111.0083	$111.01	$111.00	$111.00
Purchase #3	$241.88	3.290%	$249.8379	$249.84	$249.85	$249.80
Purchase #4	$122.89	12.584%	$138.3545	$138.35	$138.35	$138.40
Purchase #5	$61.39	9.485%	$67.2128	$67.21	$67.20	$67.20
Purchase #6	$149.45	4.781%	$156.5952	$156.60	$156.60	$156.60
Purchase #7	$213.67	4.527%	$223.3428	$223.34	$223.35	$223.30
7 purchase totals =	$979.63		$1,046.3699	$1,046.37	$1,046.35	$1,046.30