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	$171.38	11.188%	$190.554	$190.55	$190.55	$190.60
Purchase #2	$162.26	10.833%	$179.8376	$179.84	$179.85	$179.80
Purchase #3	$105.86	13.863%	$120.5354	$120.54	$120.55	$120.50
Purchase #4	$61.58	5.237%	$64.8049	$64.80	$64.80	$64.80
Purchase #5	$49.42	12.665%	$55.679	$55.68	$55.70	$55.70
Purchase #6	$19.98	3.276%	$20.6345	$20.63	$20.65	$20.60
Purchase #7	$110.93	12.231%	$124.4978	$124.50	$124.50	$124.50
7 purchase totals =	$681.41		$756.5432	$756.54	$756.60	$756.50