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	$223.79	9.387%	$244.7972	$244.80	$244.80	$244.80
Purchase #2	$141.81	10.608%	$156.8532	$156.85	$156.85	$156.90
Purchase #3	$67.57	7.258%	$72.4742	$72.47	$72.45	$72.50
Purchase #4	$164.72	9.846%	$180.9383	$180.94	$180.95	$180.90
Purchase #5	$48.50	12.255%	$54.4437	$54.44	$54.45	$54.40
Purchase #6	$220.39	10.246%	$242.9712	$242.97	$242.95	$243.00
Purchase #7	$119.75	10.427%	$132.2363	$132.24	$132.25	$132.20
7 purchase totals =	$986.53		$1,084.7141	$1,084.71	$1,084.70	$1,084.70