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	$131.40	10.768%	$145.5492	$145.55	$145.55	$145.50
Purchase #2	$149.95	10.184%	$165.2209	$165.22	$165.20	$165.20
Purchase #3	$218.68	8.485%	$237.235	$237.24	$237.25	$237.20
Purchase #4	$40.97	10.551%	$45.2927	$45.29	$45.30	$45.30
Purchase #5	$138.69	13.837%	$157.8805	$157.88	$157.90	$157.90
Purchase #6	$123.30	11.591%	$137.5917	$137.59	$137.60	$137.60
Purchase #7	$72.39	11.714%	$80.8698	$80.87	$80.85	$80.90
7 purchase totals =	$875.38		$969.6398	$969.64	$969.65	$969.60