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	$248.51	5.578%	$262.3719	$262.37	$262.35	$262.40
Purchase #2	$173.67	13.298%	$196.7646	$196.76	$196.75	$196.80
Purchase #3	$131.26	9.642%	$143.9161	$143.92	$143.90	$143.90
Purchase #4	$120.45	9.542%	$131.9433	$131.94	$131.95	$131.90
Purchase #5	$203.67	8.636%	$221.2589	$221.26	$221.25	$221.30
Purchase #6	$113.86	12.398%	$127.9764	$127.98	$128.00	$128.00
Purchase #7	$163.68	3.520%	$169.4415	$169.44	$169.45	$169.40
7 purchase totals =	$1,155.10		$1,253.6727	$1,253.67	$1,253.65	$1,253.70