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	$166.60	5.673%	$176.0512	$176.05	$176.05	$176.10
Purchase #2	$94.43	3.661%	$97.8871	$97.89	$97.90	$97.90
Purchase #3	$163.83	3.647%	$169.8049	$169.80	$169.80	$169.80
Purchase #4	$132.48	6.283%	$140.8037	$140.80	$140.80	$140.80
Purchase #5	$127.82	11.317%	$142.2854	$142.29	$142.30	$142.30
Purchase #6	$165.39	3.816%	$171.7013	$171.70	$171.70	$171.70
Purchase #7	$248.97	3.189%	$256.9097	$256.91	$256.90	$256.90
7 purchase totals =	$1,099.52		$1,155.4433	$1,155.44	$1,155.45	$1,155.50