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	$112.41	10.182%	$123.8556	$123.86	$123.85	$123.90
Purchase #2	$177.30	13.322%	$200.9199	$200.92	$200.90	$200.90
Purchase #3	$74.83	5.854%	$79.2105	$79.21	$79.20	$79.20
Purchase #4	$174.56	7.629%	$187.8772	$187.88	$187.90	$187.90
Purchase #5	$150.43	10.756%	$166.6103	$166.61	$166.60	$166.60
Purchase #6	$102.67	4.846%	$107.6454	$107.65	$107.65	$107.60
Purchase #7	$53.58	11.422%	$59.6999	$59.70	$59.70	$59.70
7 purchase totals =	$845.78		$925.8188	$925.83	$925.80	$925.80