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	$86.58	4.774%	$90.7133	$90.71	$90.70	$90.70
Purchase #2	$13.27	13.669%	$15.0839	$15.08	$15.10	$15.10
Purchase #3	$53.87	10.835%	$59.7068	$59.71	$59.70	$59.70
Purchase #4	$38.88	5.650%	$41.0767	$41.08	$41.10	$41.10
Purchase #5	$12.88	5.307%	$13.5635	$13.56	$13.55	$13.60
Purchase #6	$157.36	11.448%	$175.3746	$175.37	$175.35	$175.40
Purchase #7	$137.29	3.102%	$141.5487	$141.55	$141.55	$141.50
7 purchase totals =	$500.13		$537.0675	$537.06	$537.05	$537.10