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	$119.94	3.265%	$123.856	$123.86	$123.85	$123.90
Purchase #2	$240.67	12.478%	$270.7008	$270.70	$270.70	$270.70
Purchase #3	$40.71	6.656%	$43.4197	$43.42	$43.40	$43.40
Purchase #4	$195.73	6.741%	$208.9242	$208.92	$208.90	$208.90
Purchase #5	$59.95	7.510%	$64.4522	$64.45	$64.45	$64.50
Purchase #6	$242.78	9.634%	$266.1694	$266.17	$266.15	$266.20
Purchase #7	$80.44	4.172%	$83.796	$83.80	$83.80	$83.80
7 purchase totals =	$980.22		$1,061.3183	$1,061.32	$1,061.25	$1,061.40