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	$69.68	3.273%	$71.9606	$71.96	$71.95	$72.00
Purchase #2	$100.71	12.807%	$113.6079	$113.61	$113.60	$113.60
Purchase #3	$44.91	13.158%	$50.8193	$50.82	$50.80	$50.80
Purchase #4	$103.56	4.764%	$108.4936	$108.49	$108.50	$108.50
Purchase #5	$170.81	9.830%	$187.6006	$187.60	$187.60	$187.60
Purchase #6	$59.61	5.187%	$62.702	$62.70	$62.70	$62.70
Purchase #7	$104.45	12.802%	$117.8217	$117.82	$117.80	$117.80
7 purchase totals =	$653.73		$713.0057	$713.00	$712.95	$713.00