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	$76.48	12.780%	$86.2541	$86.25	$86.25	$86.30
Purchase #2	$14.34	4.447%	$14.9777	$14.98	$15.00	$15.00
Purchase #3	$173.64	5.141%	$182.5668	$182.57	$182.55	$182.60
Purchase #4	$200.65	7.785%	$216.2706	$216.27	$216.25	$216.30
Purchase #5	$48.94	11.587%	$54.6107	$54.61	$54.60	$54.60
Purchase #6	$18.98	4.401%	$19.8153	$19.82	$19.80	$19.80
Purchase #7	$27.59	6.315%	$29.3323	$29.33	$29.35	$29.30
7 purchase totals =	$560.62		$603.8275	$603.83	$603.80	$603.90