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	$99.71	10.476%	$110.1556	$110.16	$110.15	$110.20
Purchase #2	$82.82	10.750%	$91.7232	$91.72	$91.70	$91.70
Purchase #3	$36.76	6.339%	$39.0902	$39.09	$39.10	$39.10
Purchase #4	$23.65	3.659%	$24.5154	$24.52	$24.50	$24.50
Purchase #5	$80.35	12.803%	$90.6372	$90.64	$90.65	$90.60
Purchase #6	$42.81	3.567%	$44.337	$44.34	$44.35	$44.30
Purchase #7	$249.42	5.336%	$262.7291	$262.73	$262.75	$262.70
7 purchase totals =	$615.52		$663.1877	$663.20	$663.20	$663.10