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	$222.50	4.213%	$231.8739	$231.87	$231.85	$231.90
Purchase #2	$158.29	7.258%	$169.7787	$169.78	$169.80	$169.80
Purchase #3	$110.71	11.870%	$123.8513	$123.85	$123.85	$123.90
Purchase #4	$83.50	7.320%	$89.6122	$89.61	$89.60	$89.60
Purchase #5	$52.45	9.873%	$57.6284	$57.63	$57.65	$57.60
Purchase #6	$241.95	8.239%	$261.8843	$261.88	$261.90	$261.90
Purchase #7	$142.76	7.835%	$153.9452	$153.95	$153.95	$153.90
7 purchase totals =	$1,012.16		$1,088.5740	$1,088.57	$1,088.60	$1,088.60