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	$199.94	13.345%	$226.622	$226.62	$226.60	$226.60
Purchase #2	$192.26	5.328%	$202.5036	$202.50	$202.50	$202.50
Purchase #3	$161.69	4.546%	$169.0404	$169.04	$169.05	$169.00
Purchase #4	$227.49	5.655%	$240.3546	$240.35	$240.35	$240.40
Purchase #5	$84.32	7.168%	$90.3641	$90.36	$90.35	$90.40
Purchase #6	$75.63	3.730%	$78.451	$78.45	$78.45	$78.50
Purchase #7	$71.70	9.219%	$78.31	$78.31	$78.30	$78.30
7 purchase totals =	$1,013.03		$1,085.6457	$1,085.63	$1,085.60	$1,085.70