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	$39.42	9.641%	$43.2205	$43.22	$43.20	$43.20
Purchase #2	$12.39	8.742%	$13.4731	$13.47	$13.45	$13.50
Purchase #3	$62.61	3.261%	$64.6517	$64.65	$64.65	$64.70
Purchase #4	$84.94	6.647%	$90.586	$90.59	$90.60	$90.60
Purchase #5	$224.32	4.252%	$233.8581	$233.86	$233.85	$233.90
Purchase #6	$114.71	10.358%	$126.5917	$126.59	$126.60	$126.60
Purchase #7	$85.96	10.698%	$95.156	$95.16	$95.15	$95.20
7 purchase totals =	$624.35		$667.5371	$667.54	$667.50	$667.70