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	$142.86	10.775%	$158.2532	$158.25	$158.25	$158.30
Purchase #2	$151.95	8.442%	$164.7776	$164.78	$164.80	$164.80
Purchase #3	$53.40	11.577%	$59.5821	$59.58	$59.60	$59.60
Purchase #4	$69.50	11.266%	$77.3299	$77.33	$77.35	$77.30
Purchase #5	$34.58	8.337%	$37.4629	$37.46	$37.45	$37.50
Purchase #6	$25.74	13.371%	$29.1817	$29.18	$29.20	$29.20
Purchase #7	$70.41	7.222%	$75.495	$75.50	$75.50	$75.50
7 purchase totals =	$548.44		$602.0824	$602.08	$602.15	$602.20