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	$59.68	9.821%	$65.5412	$65.54	$65.55	$65.50
Purchase #2	$138.91	5.544%	$146.6112	$146.61	$146.60	$146.60
Purchase #3	$36.95	4.501%	$38.6131	$38.61	$38.60	$38.60
Purchase #4	$20.35	5.691%	$21.5081	$21.51	$21.50	$21.50
Purchase #5	$37.76	7.335%	$40.5297	$40.53	$40.55	$40.50
Purchase #6	$111.42	10.759%	$123.4077	$123.41	$123.40	$123.40
Purchase #7	$217.73	5.245%	$229.1499	$229.15	$229.15	$229.10
7 purchase totals =	$622.80		$665.3609	$665.36	$665.35	$665.20