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	$225.34	7.756%	$242.8174	$242.82	$242.80	$242.80
Purchase #2	$92.34	3.874%	$95.9173	$95.92	$95.90	$95.90
Purchase #3	$171.30	3.556%	$177.3914	$177.39	$177.40	$177.40
Purchase #4	$204.64	12.136%	$229.4751	$229.48	$229.50	$229.50
Purchase #5	$156.45	5.397%	$164.8936	$164.89	$164.90	$164.90
Purchase #6	$93.60	4.116%	$97.4526	$97.45	$97.45	$97.50
Purchase #7	$42.87	12.604%	$48.2733	$48.27	$48.25	$48.30
7 purchase totals =	$986.54		$1,056.2207	$1,056.22	$1,056.20	$1,056.30