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	$249.31	6.578%	$265.7096	$265.71	$265.70	$265.70
Purchase #2	$78.49	7.788%	$84.6028	$84.60	$84.60	$84.60
Purchase #3	$219.31	10.612%	$242.5832	$242.58	$242.60	$242.60
Purchase #4	$24.81	11.844%	$27.7485	$27.75	$27.75	$27.70
Purchase #5	$166.54	4.197%	$173.5297	$173.53	$173.55	$173.50
Purchase #6	$182.79	7.267%	$196.0733	$196.07	$196.05	$196.10
Purchase #7	$221.46	7.685%	$238.4792	$238.48	$238.50	$238.50
7 purchase totals =	$1,142.71		$1,228.7263	$1,228.72	$1,228.75	$1,228.70