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	$225.83	5.626%	$238.5352	$238.54	$238.55	$238.50
Purchase #2	$58.31	4.874%	$61.152	$61.15	$61.15	$61.20
Purchase #3	$140.79	13.491%	$159.784	$159.78	$159.80	$159.80
Purchase #4	$220.92	9.520%	$241.9516	$241.95	$241.95	$242.00
Purchase #5	$92.34	12.296%	$103.6941	$103.69	$103.70	$103.70
Purchase #6	$41.91	9.105%	$45.7259	$45.73	$45.75	$45.70
Purchase #7	$176.40	11.217%	$196.1868	$196.19	$196.20	$196.20
7 purchase totals =	$956.50		$1,047.0296	$1,047.03	$1,047.10	$1,047.10