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	$178.28	3.462%	$184.4521	$184.45	$184.45	$184.50
Purchase #2	$13.55	12.694%	$15.27	$15.27	$15.25	$15.30
Purchase #3	$172.65	6.763%	$184.3263	$184.33	$184.35	$184.30
Purchase #4	$210.38	9.748%	$230.8878	$230.89	$230.90	$230.90
Purchase #5	$237.53	5.143%	$249.7462	$249.75	$249.75	$249.70
Purchase #6	$213.70	4.108%	$222.4788	$222.48	$222.50	$222.50
Purchase #7	$51.58	11.230%	$57.3724	$57.37	$57.35	$57.40
7 purchase totals =	$1,077.67		$1,144.5336	$1,144.54	$1,144.55	$1,144.60