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	$167.69	13.561%	$190.4304	$190.43	$190.45	$190.40
Purchase #2	$217.49	8.717%	$236.4486	$236.45	$236.45	$236.40
Purchase #3	$241.59	13.275%	$273.6611	$273.66	$273.65	$273.70
Purchase #4	$141.47	6.346%	$150.4477	$150.45	$150.45	$150.40
Purchase #5	$147.49	13.646%	$167.6165	$167.62	$167.60	$167.60
Purchase #6	$31.69	3.547%	$32.814	$32.81	$32.80	$32.80
Purchase #7	$27.59	9.371%	$30.1755	$30.18	$30.20	$30.20
7 purchase totals =	$975.01		$1,081.5938	$1,081.60	$1,081.60	$1,081.50