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	$164.32	12.407%	$184.7072	$184.71	$184.70	$184.70
Purchase #2	$20.29	11.491%	$22.6215	$22.62	$22.60	$22.60
Purchase #3	$62.56	5.390%	$65.932	$65.93	$65.95	$65.90
Purchase #4	$172.46	13.729%	$196.137	$196.14	$196.15	$196.10
Purchase #5	$89.71	6.759%	$95.7735	$95.77	$95.75	$95.80
Purchase #6	$147.94	8.800%	$160.9587	$160.96	$160.95	$161.00
Purchase #7	$80.59	7.599%	$86.714	$86.71	$86.70	$86.70
7 purchase totals =	$737.87		$812.8439	$812.84	$812.80	$812.80