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	$183.90	9.122%	$200.6754	$200.68	$200.70	$200.70
Purchase #2	$107.48	8.425%	$116.5352	$116.54	$116.55	$116.50
Purchase #3	$139.36	8.273%	$150.8893	$150.89	$150.90	$150.90
Purchase #4	$211.54	5.553%	$223.2868	$223.29	$223.30	$223.30
Purchase #5	$200.91	13.116%	$227.2614	$227.26	$227.25	$227.30
Purchase #6	$108.43	10.147%	$119.4324	$119.43	$119.45	$119.40
Purchase #7	$199.36	10.741%	$220.7733	$220.77	$220.75	$220.80
7 purchase totals =	$1,150.98		$1,258.8538	$1,258.86	$1,258.90	$1,258.90