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	$217.29	10.826%	$240.8138	$240.81	$240.80	$240.80
Purchase #2	$172.32	11.316%	$191.8197	$191.82	$191.80	$191.80
Purchase #3	$83.86	9.599%	$91.9097	$91.91	$91.90	$91.90
Purchase #4	$177.50	7.601%	$190.9918	$190.99	$191.00	$191.00
Purchase #5	$182.45	13.164%	$206.4677	$206.47	$206.45	$206.50
Purchase #6	$150.40	9.431%	$164.5842	$164.58	$164.60	$164.60
Purchase #7	$172.64	13.792%	$196.4505	$196.45	$196.45	$196.50
7 purchase totals =	$1,156.46		$1,283.0374	$1,283.03	$1,283.00	$1,283.10