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	$118.81	11.510%	$132.485	$132.49	$132.50	$132.50
Purchase #2	$74.71	12.299%	$83.8986	$83.90	$83.90	$83.90
Purchase #3	$129.32	6.627%	$137.89	$137.89	$137.90	$137.90
Purchase #4	$36.72	9.809%	$40.3219	$40.32	$40.30	$40.30
Purchase #5	$133.75	10.352%	$147.5958	$147.60	$147.60	$147.60
Purchase #6	$131.39	12.487%	$147.7967	$147.80	$147.80	$147.80
Purchase #7	$60.68	12.150%	$68.0526	$68.05	$68.05	$68.10
7 purchase totals =	$685.38		$758.0406	$758.05	$758.05	$758.10