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	$60.90	10.380%	$67.2214	$67.22	$67.20	$67.20
Purchase #2	$147.45	9.862%	$161.9915	$161.99	$162.00	$162.00
Purchase #3	$133.95	3.661%	$138.8539	$138.85	$138.85	$138.90
Purchase #4	$160.33	3.264%	$165.5632	$165.56	$165.55	$165.60
Purchase #5	$55.26	7.592%	$59.4553	$59.46	$59.45	$59.50
Purchase #6	$217.41	11.208%	$241.7773	$241.78	$241.80	$241.80
Purchase #7	$11.85	4.874%	$12.4276	$12.43	$12.45	$12.40
7 purchase totals =	$787.15		$847.2902	$847.29	$847.30	$847.40