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	$100.52	11.134%	$111.7119	$111.71	$111.70	$111.70
Purchase #2	$110.60	9.835%	$121.4775	$121.48	$121.50	$121.50
Purchase #3	$242.48	4.246%	$252.7757	$252.78	$252.80	$252.80
Purchase #4	$92.72	8.770%	$100.8515	$100.85	$100.85	$100.90
Purchase #5	$75.70	12.682%	$85.3003	$85.30	$85.30	$85.30
Purchase #6	$221.54	10.383%	$244.5425	$244.54	$244.55	$244.50
Purchase #7	$84.65	9.800%	$92.9457	$92.95	$92.95	$92.90
7 purchase totals =	$928.21		$1,009.6051	$1,009.61	$1,009.65	$1,009.60