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	$31.92	5.782%	$33.7656	$33.77	$33.75	$33.80
Purchase #2	$155.46	11.527%	$173.3799	$173.38	$173.40	$173.40
Purchase #3	$238.26	10.344%	$262.9056	$262.91	$262.90	$262.90
Purchase #4	$207.31	12.195%	$232.5915	$232.59	$232.60	$232.60
Purchase #5	$35.34	11.652%	$39.4578	$39.46	$39.45	$39.50
Purchase #6	$239.82	13.190%	$271.4523	$271.45	$271.45	$271.50
Purchase #7	$43.74	10.678%	$48.4106	$48.41	$48.40	$48.40
7 purchase totals =	$951.85		$1,061.9633	$1,061.97	$1,061.95	$1,062.10