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	$213.88	3.837%	$222.0866	$222.09	$222.10	$222.10
Purchase #2	$86.78	12.567%	$97.6856	$97.69	$97.70	$97.70
Purchase #3	$144.73	11.169%	$160.8949	$160.89	$160.90	$160.90
Purchase #4	$105.76	6.492%	$112.6259	$112.63	$112.65	$112.60
Purchase #5	$187.29	10.210%	$206.4123	$206.41	$206.40	$206.40
Purchase #6	$48.29	10.833%	$53.5213	$53.52	$53.50	$53.50
Purchase #7	$139.86	8.396%	$151.6026	$151.60	$151.60	$151.60
7 purchase totals =	$926.59		$1,004.8292	$1,004.83	$1,004.85	$1,004.80