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	$87.38	12.837%	$98.597	$98.60	$98.60	$98.60
Purchase #2	$23.25	10.261%	$25.6357	$25.64	$25.65	$25.60
Purchase #3	$33.91	11.771%	$37.9015	$37.90	$37.90	$37.90
Purchase #4	$228.90	11.787%	$255.8804	$255.88	$255.90	$255.90
Purchase #5	$67.40	10.636%	$74.5687	$74.57	$74.55	$74.60
Purchase #6	$28.85	3.504%	$29.8609	$29.86	$29.85	$29.90
Purchase #7	$29.83	12.326%	$33.5068	$33.51	$33.50	$33.50
7 purchase totals =	$499.52		$555.9510	$555.96	$555.95	$556.00