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	$178.50	10.306%	$196.8962	$196.90	$196.90	$196.90
Purchase #2	$139.64	11.853%	$156.1915	$156.19	$156.20	$156.20
Purchase #3	$234.34	9.435%	$256.45	$256.45	$256.45	$256.50
Purchase #4	$92.88	9.447%	$101.6544	$101.65	$101.65	$101.70
Purchase #5	$219.94	9.121%	$240.0007	$240.00	$240.00	$240.00
Purchase #6	$10.91	6.103%	$11.5758	$11.58	$11.60	$11.60
Purchase #7	$66.67	6.171%	$70.7842	$70.78	$70.80	$70.80
7 purchase totals =	$942.88		$1,033.5528	$1,033.55	$1,033.60	$1,033.70