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	$198.37	5.241%	$208.7666	$208.77	$208.75	$208.80
Purchase #2	$194.45	9.371%	$212.6719	$212.67	$212.65	$212.70
Purchase #3	$217.94	7.720%	$234.765	$234.77	$234.75	$234.80
Purchase #4	$240.94	6.363%	$256.271	$256.27	$256.25	$256.30
Purchase #5	$47.39	11.810%	$52.9868	$52.99	$53.00	$53.00
Purchase #6	$99.85	3.370%	$103.2149	$103.21	$103.20	$103.20
Purchase #7	$29.48	6.720%	$31.4611	$31.46	$31.45	$31.50
7 purchase totals =	$1,028.42		$1,100.1373	$1,100.14	$1,100.05	$1,100.30