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	$101.59	13.113%	$114.9115	$114.91	$114.90	$114.90
Purchase #2	$78.44	5.723%	$82.9291	$82.93	$82.95	$82.90
Purchase #3	$153.28	4.195%	$159.7101	$159.71	$159.70	$159.70
Purchase #4	$249.37	9.713%	$273.5913	$273.59	$273.60	$273.60
Purchase #5	$163.42	11.869%	$182.8163	$182.82	$182.80	$182.80
Purchase #6	$185.59	11.476%	$206.8883	$206.89	$206.90	$206.90
Purchase #7	$71.56	10.406%	$79.0065	$79.01	$79.00	$79.00
7 purchase totals =	$1,003.25		$1,099.8531	$1,099.86	$1,099.85	$1,099.80