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	$168.77	12.714%	$190.2274	$190.23	$190.25	$190.20
Purchase #2	$48.43	4.287%	$50.5062	$50.51	$50.50	$50.50
Purchase #3	$77.46	11.691%	$86.5158	$86.52	$86.50	$86.50
Purchase #4	$168.60	5.296%	$177.5291	$177.53	$177.55	$177.50
Purchase #5	$54.34	8.397%	$58.9029	$58.90	$58.90	$58.90
Purchase #6	$248.49	7.275%	$266.5676	$266.57	$266.55	$266.60
Purchase #7	$179.31	11.743%	$200.3664	$200.37	$200.35	$200.40
7 purchase totals =	$945.40		$1,030.6154	$1,030.63	$1,030.60	$1,030.60