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	$131.98	10.124%	$145.3417	$145.34	$145.35	$145.30
Purchase #2	$132.82	13.701%	$151.0177	$151.02	$151.00	$151.00
Purchase #3	$132.45	6.814%	$141.4751	$141.48	$141.50	$141.50
Purchase #4	$207.81	10.386%	$229.3931	$229.39	$229.40	$229.40
Purchase #5	$18.79	6.113%	$19.9386	$19.94	$19.95	$19.90
Purchase #6	$125.29	9.208%	$136.8267	$136.83	$136.85	$136.80
Purchase #7	$190.86	9.835%	$209.6311	$209.63	$209.65	$209.60
7 purchase totals =	$940.00		$1,033.6240	$1,033.63	$1,033.70	$1,033.50