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	$44.48	7.416%	$47.7786	$47.78	$47.80	$47.80
Purchase #2	$214.78	4.492%	$224.4279	$224.43	$224.45	$224.40
Purchase #3	$205.86	8.646%	$223.6587	$223.66	$223.65	$223.70
Purchase #4	$197.43	13.768%	$224.6122	$224.61	$224.60	$224.60
Purchase #5	$219.31	7.266%	$235.2451	$235.25	$235.25	$235.20
Purchase #6	$66.89	8.593%	$72.6379	$72.64	$72.65	$72.60
Purchase #7	$103.42	7.450%	$111.1248	$111.12	$111.10	$111.10
7 purchase totals =	$1,052.17		$1,139.4852	$1,139.49	$1,139.50	$1,139.40