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	$54.73	13.776%	$62.2696	$62.27	$62.25	$62.30
Purchase #2	$232.47	9.735%	$255.101	$255.10	$255.10	$255.10
Purchase #3	$95.78	3.396%	$99.0327	$99.03	$99.05	$99.00
Purchase #4	$164.33	12.713%	$185.2213	$185.22	$185.20	$185.20
Purchase #5	$245.25	4.102%	$255.3102	$255.31	$255.30	$255.30
Purchase #6	$240.63	10.807%	$266.6349	$266.63	$266.65	$266.60
Purchase #7	$6.39	10.355%	$7.0517	$7.05	$7.05	$7.10
7 purchase totals =	$1,039.58		$1,130.6214	$1,130.61	$1,130.60	$1,130.60