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	$187.29	11.405%	$208.6504	$208.65	$208.65	$208.70
Purchase #2	$202.91	5.698%	$214.4718	$214.47	$214.45	$214.50
Purchase #3	$162.80	7.189%	$174.5037	$174.50	$174.50	$174.50
Purchase #4	$78.60	5.225%	$82.7069	$82.71	$82.70	$82.70
Purchase #5	$130.69	8.368%	$141.6261	$141.63	$141.65	$141.60
Purchase #6	$52.62	8.312%	$56.9938	$56.99	$57.00	$57.00
Purchase #7	$90.88	9.563%	$99.5709	$99.57	$99.55	$99.60
7 purchase totals =	$905.79		$978.5236	$978.52	$978.50	$978.60