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	$201.51	3.242%	$208.043	$208.04	$208.05	$208.00
Purchase #2	$111.27	3.778%	$115.4738	$115.47	$115.45	$115.50
Purchase #3	$80.80	6.242%	$85.8435	$85.84	$85.85	$85.80
Purchase #4	$249.38	9.771%	$273.7469	$273.75	$273.75	$273.70
Purchase #5	$52.44	3.273%	$54.1564	$54.16	$54.15	$54.20
Purchase #6	$228.41	6.124%	$242.3978	$242.40	$242.40	$242.40
Purchase #7	$176.59	9.206%	$192.8469	$192.85	$192.85	$192.80
7 purchase totals =	$1,100.40		$1,172.5083	$1,172.51	$1,172.50	$1,172.40