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	$111.85	10.665%	$123.7788	$123.78	$123.80	$123.80
Purchase #2	$13.65	5.427%	$14.3908	$14.39	$14.40	$14.40
Purchase #3	$209.60	7.295%	$224.8903	$224.89	$224.90	$224.90
Purchase #4	$181.33	7.339%	$194.6378	$194.64	$194.65	$194.60
Purchase #5	$92.82	12.834%	$104.7325	$104.73	$104.75	$104.70
Purchase #6	$56.53	13.866%	$64.3684	$64.37	$64.35	$64.40
Purchase #7	$136.41	12.665%	$153.6863	$153.69	$153.70	$153.70
7 purchase totals =	$802.19		$880.4849	$880.49	$880.55	$880.50