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	$69.98	4.249%	$72.9535	$72.95	$72.95	$73.00
Purchase #2	$233.39	12.627%	$262.8602	$262.86	$262.85	$262.90
Purchase #3	$237.91	10.402%	$262.6574	$262.66	$262.65	$262.70
Purchase #4	$55.57	10.167%	$61.2198	$61.22	$61.20	$61.20
Purchase #5	$132.68	12.179%	$148.8391	$148.84	$148.85	$148.80
Purchase #6	$43.95	4.170%	$45.7827	$45.78	$45.80	$45.80
Purchase #7	$219.86	5.593%	$232.1568	$232.16	$232.15	$232.20
7 purchase totals =	$993.34		$1,086.4695	$1,086.47	$1,086.45	$1,086.60