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	$218.96	4.297%	$228.3687	$228.37	$228.35	$228.40
Purchase #2	$181.82	4.768%	$190.4892	$190.49	$190.50	$190.50
Purchase #3	$40.89	3.616%	$42.3686	$42.37	$42.35	$42.40
Purchase #4	$127.68	12.604%	$143.7728	$143.77	$143.75	$143.80
Purchase #5	$62.39	11.693%	$69.6853	$69.69	$69.70	$69.70
Purchase #6	$156.32	11.301%	$173.9857	$173.99	$174.00	$174.00
Purchase #7	$16.92	11.210%	$18.8167	$18.82	$18.80	$18.80
7 purchase totals =	$804.98		$867.4870	$867.50	$867.45	$867.60