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	$229.45	9.542%	$251.3441	$251.34	$251.35	$251.30
Purchase #2	$79.68	11.559%	$88.8902	$88.89	$88.90	$88.90
Purchase #3	$76.35	5.737%	$80.7302	$80.73	$80.75	$80.70
Purchase #4	$213.65	9.435%	$233.8079	$233.81	$233.80	$233.80
Purchase #5	$97.78	13.531%	$111.0106	$111.01	$111.00	$111.00
Purchase #6	$233.47	3.632%	$241.9496	$241.95	$241.95	$241.90
Purchase #7	$92.46	3.135%	$95.3586	$95.36	$95.35	$95.40
7 purchase totals =	$1,022.84		$1,103.0912	$1,103.09	$1,103.10	$1,103.00