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	$205.38	5.463%	$216.5999	$216.60	$216.60	$216.60
Purchase #2	$247.59	3.215%	$255.55	$255.55	$255.55	$255.60
Purchase #3	$195.38	9.486%	$213.9137	$213.91	$213.90	$213.90
Purchase #4	$229.25	13.823%	$260.9392	$260.94	$260.95	$260.90
Purchase #5	$166.91	10.119%	$183.7996	$183.80	$183.80	$183.80
Purchase #6	$78.90	12.725%	$88.94	$88.94	$88.95	$88.90
Purchase #7	$82.51	10.817%	$91.4351	$91.44	$91.45	$91.40
7 purchase totals =	$1,205.92		$1,311.1775	$1,311.18	$1,311.20	$1,311.10