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	$137.84	9.496%	$150.9293	$150.93	$150.95	$150.90
Purchase #2	$202.89	7.194%	$217.4859	$217.49	$217.50	$217.50
Purchase #3	$190.80	9.351%	$208.6417	$208.64	$208.65	$208.60
Purchase #4	$10.36	12.824%	$11.6886	$11.69	$11.70	$11.70
Purchase #5	$154.41	8.491%	$167.521	$167.52	$167.50	$167.50
Purchase #6	$36.49	4.696%	$38.2036	$38.20	$38.20	$38.20
Purchase #7	$211.36	5.730%	$223.4709	$223.47	$223.45	$223.50
7 purchase totals =	$944.15		$1,017.9410	$1,017.94	$1,017.95	$1,017.90