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	$158.45	8.267%	$171.5491	$171.55	$171.55	$171.50
Purchase #2	$213.72	3.594%	$221.4011	$221.40	$221.40	$221.40
Purchase #3	$87.85	13.427%	$99.6456	$99.65	$99.65	$99.60
Purchase #4	$187.97	4.526%	$196.4775	$196.48	$196.50	$196.50
Purchase #5	$116.64	10.267%	$128.6154	$128.62	$128.60	$128.60
Purchase #6	$97.33	3.325%	$100.5662	$100.57	$100.55	$100.60
Purchase #7	$117.45	6.647%	$125.2569	$125.26	$125.25	$125.30
7 purchase totals =	$979.41		$1,043.5118	$1,043.53	$1,043.50	$1,043.50