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	$120.85	3.178%	$124.6906	$124.69	$124.70	$124.70
Purchase #2	$25.80	11.757%	$28.8333	$28.83	$28.85	$28.80
Purchase #3	$38.85	12.253%	$43.6103	$43.61	$43.60	$43.60
Purchase #4	$12.25	13.257%	$13.874	$13.87	$13.85	$13.90
Purchase #5	$176.53	6.168%	$187.4184	$187.42	$187.40	$187.40
Purchase #6	$248.77	5.727%	$263.0171	$263.02	$263.00	$263.00
Purchase #7	$223.83	3.315%	$231.25	$231.25	$231.25	$231.30
7 purchase totals =	$846.88		$892.6937	$892.69	$892.65	$892.70