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	$113.36	3.678%	$117.5294	$117.53	$117.55	$117.50
Purchase #2	$250.49	13.213%	$283.5872	$283.59	$283.60	$283.60
Purchase #3	$186.41	3.317%	$192.5932	$192.59	$192.60	$192.60
Purchase #4	$126.66	12.139%	$142.0353	$142.04	$142.05	$142.00
Purchase #5	$34.34	13.350%	$38.9244	$38.92	$38.90	$38.90
Purchase #6	$132.50	6.520%	$141.139	$141.14	$141.15	$141.10
Purchase #7	$151.96	7.120%	$162.7796	$162.78	$162.80	$162.80
7 purchase totals =	$995.72		$1,078.5881	$1,078.59	$1,078.65	$1,078.50