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	$152.77	3.667%	$158.3721	$158.37	$158.35	$158.40
Purchase #2	$139.80	4.698%	$146.3678	$146.37	$146.35	$146.40
Purchase #3	$123.87	13.421%	$140.4946	$140.49	$140.50	$140.50
Purchase #4	$184.62	7.337%	$198.1656	$198.17	$198.15	$198.20
Purchase #5	$118.32	8.502%	$128.3796	$128.38	$128.40	$128.40
Purchase #6	$6.27	10.798%	$6.947	$6.95	$6.95	$6.90
Purchase #7	$111.59	8.156%	$120.6913	$120.69	$120.70	$120.70
7 purchase totals =	$837.24		$899.4180	$899.42	$899.40	$899.50