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	$158.31	7.159%	$169.6434	$169.64	$169.65	$169.60
Purchase #2	$226.31	13.228%	$256.2463	$256.25	$256.25	$256.20
Purchase #3	$231.49	4.576%	$242.083	$242.08	$242.10	$242.10
Purchase #4	$6.65	13.448%	$7.5443	$7.54	$7.55	$7.50
Purchase #5	$64.46	4.865%	$67.596	$67.60	$67.60	$67.60
Purchase #6	$96.35	4.710%	$100.8881	$100.89	$100.90	$100.90
Purchase #7	$112.85	12.155%	$126.5669	$126.57	$126.55	$126.60
7 purchase totals =	$896.42		$970.5680	$970.57	$970.60	$970.50