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	$109.31	13.411%	$123.9696	$123.97	$123.95	$124.00
Purchase #2	$89.61	4.863%	$93.9677	$93.97	$93.95	$94.00
Purchase #3	$65.88	8.174%	$71.265	$71.27	$71.25	$71.30
Purchase #4	$105.38	13.574%	$119.6843	$119.68	$119.70	$119.70
Purchase #5	$168.69	6.426%	$179.53	$179.53	$179.55	$179.50
Purchase #6	$138.77	10.326%	$153.0994	$153.10	$153.10	$153.10
Purchase #7	$215.83	11.482%	$240.6116	$240.61	$240.60	$240.60
7 purchase totals =	$893.47		$982.1276	$982.13	$982.10	$982.20