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	$132.60	7.364%	$142.3647	$142.36	$142.35	$142.40
Purchase #2	$115.90	12.269%	$130.1198	$130.12	$130.10	$130.10
Purchase #3	$103.29	4.583%	$108.0238	$108.02	$108.00	$108.00
Purchase #4	$14.48	10.108%	$15.9436	$15.94	$15.95	$15.90
Purchase #5	$77.99	9.769%	$85.6088	$85.61	$85.60	$85.60
Purchase #6	$156.37	3.774%	$162.2714	$162.27	$162.25	$162.30
Purchase #7	$105.28	8.593%	$114.3267	$114.33	$114.35	$114.30
7 purchase totals =	$705.91		$758.6588	$758.65	$758.60	$758.60