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	$113.57	5.214%	$119.4915	$119.49	$119.50	$119.50
Purchase #2	$25.95	11.818%	$29.0168	$29.02	$29.00	$29.00
Purchase #3	$115.66	10.146%	$127.3949	$127.39	$127.40	$127.40
Purchase #4	$32.61	5.860%	$34.5209	$34.52	$34.50	$34.50
Purchase #5	$83.59	10.274%	$92.178	$92.18	$92.20	$92.20
Purchase #6	$191.65	5.656%	$202.4897	$202.49	$202.50	$202.50
Purchase #7	$70.78	10.858%	$78.4653	$78.47	$78.45	$78.50
7 purchase totals =	$633.81		$683.5571	$683.56	$683.55	$683.60