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	$140.28	13.656%	$159.4366	$159.44	$159.45	$159.40
Purchase #2	$121.78	9.168%	$132.9448	$132.94	$132.95	$132.90
Purchase #3	$171.86	5.155%	$180.7194	$180.72	$180.70	$180.70
Purchase #4	$158.49	13.776%	$180.3236	$180.32	$180.30	$180.30
Purchase #5	$12.74	12.814%	$14.3725	$14.37	$14.35	$14.40
Purchase #6	$95.54	4.530%	$99.868	$99.87	$99.85	$99.90
Purchase #7	$248.72	12.492%	$279.7901	$279.79	$279.80	$279.80
7 purchase totals =	$949.41		$1,047.4550	$1,047.45	$1,047.40	$1,047.40