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	$218.74	9.493%	$239.505	$239.51	$239.50	$239.50
Purchase #2	$39.58	11.830%	$44.2623	$44.26	$44.25	$44.30
Purchase #3	$241.98	6.674%	$258.1297	$258.13	$258.15	$258.10
Purchase #4	$60.40	4.134%	$62.8969	$62.90	$62.90	$62.90
Purchase #5	$57.31	3.458%	$59.2918	$59.29	$59.30	$59.30
Purchase #6	$61.84	10.510%	$68.3394	$68.34	$68.35	$68.30
Purchase #7	$222.87	6.516%	$237.3922	$237.39	$237.40	$237.40
7 purchase totals =	$902.72		$969.8173	$969.82	$969.85	$969.80