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	$108.38	4.364%	$113.1097	$113.11	$113.10	$113.10
Purchase #2	$27.65	13.833%	$31.4748	$31.47	$31.45	$31.50
Purchase #3	$51.49	5.231%	$54.1834	$54.18	$54.20	$54.20
Purchase #4	$238.35	5.643%	$251.8001	$251.80	$251.80	$251.80
Purchase #5	$248.34	13.560%	$282.0149	$282.01	$282.00	$282.00
Purchase #6	$223.27	12.197%	$250.5022	$250.50	$250.50	$250.50
Purchase #7	$106.81	6.283%	$113.5209	$113.52	$113.50	$113.50
7 purchase totals =	$1,004.29		$1,096.6060	$1,096.59	$1,096.55	$1,096.60