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	$155.50	10.536%	$171.8835	$171.88	$171.90	$171.90
Purchase #2	$181.97	13.257%	$206.0938	$206.09	$206.10	$206.10
Purchase #3	$55.72	3.401%	$57.615	$57.62	$57.60	$57.60
Purchase #4	$228.40	12.137%	$256.1209	$256.12	$256.10	$256.10
Purchase #5	$152.67	7.152%	$163.589	$163.59	$163.60	$163.60
Purchase #6	$180.72	8.682%	$196.4101	$196.41	$196.40	$196.40
Purchase #7	$160.25	11.523%	$178.7156	$178.72	$178.70	$178.70
7 purchase totals =	$1,115.23		$1,230.4279	$1,230.43	$1,230.40	$1,230.40