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	$223.75	3.505%	$231.5924	$231.59	$231.60	$231.60
Purchase #2	$103.54	3.703%	$107.3741	$107.37	$107.35	$107.40
Purchase #3	$167.81	10.106%	$184.7689	$184.77	$184.75	$184.80
Purchase #4	$225.38	7.656%	$242.6351	$242.64	$242.65	$242.60
Purchase #5	$10.52	12.360%	$11.8203	$11.82	$11.80	$11.80
Purchase #6	$20.40	7.502%	$21.9304	$21.93	$21.95	$21.90
Purchase #7	$242.35	5.392%	$255.4175	$255.42	$255.40	$255.40
7 purchase totals =	$993.75		$1,055.5387	$1,055.54	$1,055.50	$1,055.50