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	$33.58	11.484%	$37.4363	$37.44	$37.45	$37.40
Purchase #2	$36.83	10.380%	$40.653	$40.65	$40.65	$40.70
Purchase #3	$86.86	4.188%	$90.4977	$90.50	$90.50	$90.50
Purchase #4	$207.74	10.803%	$230.1822	$230.18	$230.20	$230.20
Purchase #5	$193.78	11.685%	$216.4232	$216.42	$216.40	$216.40
Purchase #6	$80.54	7.389%	$86.4911	$86.49	$86.50	$86.50
Purchase #7	$38.57	10.177%	$42.4953	$42.50	$42.50	$42.50
7 purchase totals =	$677.90		$744.1788	$744.18	$744.20	$744.20