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	$244.77	8.268%	$265.0076	$265.01	$265.00	$265.00
Purchase #2	$98.54	11.455%	$109.8278	$109.83	$109.85	$109.80
Purchase #3	$119.95	5.438%	$126.4729	$126.47	$126.45	$126.50
Purchase #4	$222.83	3.532%	$230.7004	$230.70	$230.70	$230.70
Purchase #5	$173.57	3.263%	$179.2336	$179.23	$179.25	$179.20
Purchase #6	$169.32	7.428%	$181.8971	$181.90	$181.90	$181.90
Purchase #7	$44.93	13.133%	$50.8307	$50.83	$50.85	$50.80
7 purchase totals =	$1,073.91		$1,143.9701	$1,143.97	$1,144.00	$1,143.90