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	$118.43	5.114%	$124.4865	$124.49	$124.50	$124.50
Purchase #2	$133.51	10.774%	$147.8944	$147.89	$147.90	$147.90
Purchase #3	$57.71	3.268%	$59.596	$59.60	$59.60	$59.60
Purchase #4	$224.58	7.739%	$241.9602	$241.96	$241.95	$242.00
Purchase #5	$71.64	9.593%	$78.5124	$78.51	$78.50	$78.50
Purchase #6	$225.32	7.346%	$241.872	$241.87	$241.85	$241.90
Purchase #7	$145.74	12.313%	$163.685	$163.69	$163.70	$163.70
7 purchase totals =	$976.93		$1,058.0065	$1,058.01	$1,058.00	$1,058.10