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	$179.57	12.838%	$202.6232	$202.62	$202.60	$202.60
Purchase #2	$78.86	3.319%	$81.4774	$81.48	$81.50	$81.50
Purchase #3	$237.39	9.792%	$260.6352	$260.64	$260.65	$260.60
Purchase #4	$158.84	9.378%	$173.736	$173.74	$173.75	$173.70
Purchase #5	$162.53	13.760%	$184.8941	$184.89	$184.90	$184.90
Purchase #6	$83.86	3.163%	$86.5125	$86.51	$86.50	$86.50
Purchase #7	$109.44	11.102%	$121.59	$121.59	$121.60	$121.60
7 purchase totals =	$1,010.49		$1,111.4684	$1,111.47	$1,111.50	$1,111.40