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	$102.25	4.256%	$106.6018	$106.60	$106.60	$106.60
Purchase #2	$86.61	4.151%	$90.2052	$90.21	$90.20	$90.20
Purchase #3	$107.66	4.744%	$112.7674	$112.77	$112.75	$112.80
Purchase #4	$138.91	13.826%	$158.1157	$158.12	$158.10	$158.10
Purchase #5	$44.57	8.595%	$48.4008	$48.40	$48.40	$48.40
Purchase #6	$149.30	8.834%	$162.4892	$162.49	$162.50	$162.50
Purchase #7	$199.79	11.274%	$222.3143	$222.31	$222.30	$222.30
7 purchase totals =	$829.09		$900.8944	$900.90	$900.85	$900.90