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	$124.94	5.447%	$131.7455	$131.75	$131.75	$131.70
Purchase #2	$107.92	11.857%	$120.7161	$120.72	$120.70	$120.70
Purchase #3	$184.66	11.378%	$205.6706	$205.67	$205.65	$205.70
Purchase #4	$214.87	3.127%	$221.589	$221.59	$221.60	$221.60
Purchase #5	$199.49	9.437%	$218.3159	$218.32	$218.30	$218.30
Purchase #6	$156.28	7.428%	$167.8885	$167.89	$167.90	$167.90
Purchase #7	$29.55	10.258%	$32.5812	$32.58	$32.60	$32.60
7 purchase totals =	$1,017.71		$1,098.5068	$1,098.52	$1,098.50	$1,098.50