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	$119.77	9.762%	$131.4619	$131.46	$131.45	$131.50
Purchase #2	$174.75	10.370%	$192.8716	$192.87	$192.85	$192.90
Purchase #3	$149.42	12.436%	$168.0019	$168.00	$168.00	$168.00
Purchase #4	$137.43	3.424%	$142.1356	$142.14	$142.15	$142.10
Purchase #5	$217.42	8.725%	$236.3899	$236.39	$236.40	$236.40
Purchase #6	$140.89	7.448%	$151.3835	$151.38	$151.40	$151.40
Purchase #7	$113.88	7.620%	$122.5577	$122.56	$122.55	$122.60
7 purchase totals =	$1,053.56		$1,144.8021	$1,144.80	$1,144.80	$1,144.90