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	$149.76	5.249%	$157.6209	$157.62	$157.60	$157.60
Purchase #2	$36.75	8.698%	$39.9465	$39.95	$39.95	$39.90
Purchase #3	$100.78	4.690%	$105.5066	$105.51	$105.50	$105.50
Purchase #4	$59.77	4.701%	$62.5798	$62.58	$62.60	$62.60
Purchase #5	$130.61	4.552%	$136.5554	$136.56	$136.55	$136.60
Purchase #6	$90.65	3.244%	$93.5907	$93.59	$93.60	$93.60
Purchase #7	$218.55	4.620%	$228.647	$228.65	$228.65	$228.60
7 purchase totals =	$786.87		$824.4469	$824.46	$824.45	$824.40