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	$162.60	3.577%	$168.4162	$168.42	$168.40	$168.40
Purchase #2	$55.47	11.663%	$61.9395	$61.94	$61.95	$61.90
Purchase #3	$167.42	4.136%	$174.3445	$174.34	$174.35	$174.30
Purchase #4	$146.61	8.117%	$158.5103	$158.51	$158.50	$158.50
Purchase #5	$208.88	8.850%	$227.3659	$227.37	$227.35	$227.40
Purchase #6	$75.85	10.716%	$83.9781	$83.98	$84.00	$84.00
Purchase #7	$38.41	3.796%	$39.868	$39.87	$39.85	$39.90
7 purchase totals =	$855.24		$914.4225	$914.43	$914.40	$914.40