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	$112.77	7.874%	$121.6495	$121.65	$121.65	$121.60
Purchase #2	$73.89	6.553%	$78.732	$78.73	$78.75	$78.70
Purchase #3	$199.32	13.644%	$226.5152	$226.52	$226.50	$226.50
Purchase #4	$196.77	10.341%	$217.118	$217.12	$217.10	$217.10
Purchase #5	$246.28	4.601%	$257.6113	$257.61	$257.60	$257.60
Purchase #6	$54.93	5.280%	$57.8303	$57.83	$57.85	$57.80
Purchase #7	$89.54	11.814%	$100.1183	$100.12	$100.10	$100.10
7 purchase totals =	$973.50		$1,059.5746	$1,059.58	$1,059.55	$1,059.40