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	$224.41	4.455%	$234.4075	$234.41	$234.40	$234.40
Purchase #2	$72.94	6.619%	$77.7679	$77.77	$77.75	$77.80
Purchase #3	$199.57	9.683%	$218.8944	$218.89	$218.90	$218.90
Purchase #4	$165.98	4.559%	$173.547	$173.55	$173.55	$173.50
Purchase #5	$131.95	3.517%	$136.5907	$136.59	$136.60	$136.60
Purchase #6	$102.81	5.419%	$108.3813	$108.38	$108.40	$108.40
Purchase #7	$69.80	3.739%	$72.4098	$72.41	$72.40	$72.40
7 purchase totals =	$967.46		$1,021.9986	$1,022.00	$1,022.00	$1,022.00