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	$55.85	3.578%	$57.8483	$57.85	$57.85	$57.80
Purchase #2	$154.59	5.454%	$163.0213	$163.02	$163.00	$163.00
Purchase #3	$15.94	5.353%	$16.7933	$16.79	$16.80	$16.80
Purchase #4	$50.90	3.348%	$52.6041	$52.60	$52.60	$52.60
Purchase #5	$161.85	6.709%	$172.7085	$172.71	$172.70	$172.70
Purchase #6	$85.45	5.806%	$90.4112	$90.41	$90.40	$90.40
Purchase #7	$142.60	11.611%	$159.1573	$159.16	$159.15	$159.20
7 purchase totals =	$667.18		$712.5440	$712.54	$712.50	$712.50