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	$231.49	13.369%	$262.4379	$262.44	$262.45	$262.40
Purchase #2	$59.59	4.718%	$62.4015	$62.40	$62.40	$62.40
Purchase #3	$49.43	4.210%	$51.511	$51.51	$51.50	$51.50
Purchase #4	$163.46	4.291%	$170.4741	$170.47	$170.45	$170.50
Purchase #5	$67.62	7.280%	$72.5427	$72.54	$72.55	$72.50
Purchase #6	$217.78	11.563%	$242.9619	$242.96	$242.95	$243.00
Purchase #7	$31.68	8.227%	$34.2863	$34.29	$34.30	$34.30
7 purchase totals =	$821.05		$896.6154	$896.61	$896.60	$896.60