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	$212.29	11.393%	$236.4762	$236.48	$236.50	$236.50
Purchase #2	$146.30	12.241%	$164.2086	$164.21	$164.20	$164.20
Purchase #3	$145.52	13.640%	$165.3689	$165.37	$165.35	$165.40
Purchase #4	$49.53	12.264%	$55.6044	$55.60	$55.60	$55.60
Purchase #5	$35.95	5.577%	$37.9549	$37.95	$37.95	$38.00
Purchase #6	$147.71	6.561%	$157.4013	$157.40	$157.40	$157.40
Purchase #7	$192.86	11.778%	$215.5751	$215.58	$215.60	$215.60
7 purchase totals =	$930.16		$1,032.5894	$1,032.59	$1,032.60	$1,032.70