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	$49.42	4.409%	$51.5989	$51.60	$51.60	$51.60
Purchase #2	$104.94	7.386%	$112.6909	$112.69	$112.70	$112.70
Purchase #3	$90.74	4.576%	$94.8923	$94.89	$94.90	$94.90
Purchase #4	$106.36	12.773%	$119.9454	$119.95	$119.95	$119.90
Purchase #5	$209.53	6.201%	$222.523	$222.52	$222.50	$222.50
Purchase #6	$186.97	5.158%	$196.6139	$196.61	$196.60	$196.60
Purchase #7	$137.55	8.630%	$149.4206	$149.42	$149.40	$149.40
7 purchase totals =	$885.51		$947.6850	$947.68	$947.65	$947.60