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	$155.88	7.675%	$167.8438	$167.84	$167.85	$167.80
Purchase #2	$85.96	5.247%	$90.4703	$90.47	$90.45	$90.50
Purchase #3	$221.27	3.716%	$229.4924	$229.49	$229.50	$229.50
Purchase #4	$42.80	13.270%	$48.4796	$48.48	$48.50	$48.50
Purchase #5	$37.81	11.398%	$42.1196	$42.12	$42.10	$42.10
Purchase #6	$241.86	8.299%	$261.932	$261.93	$261.95	$261.90
Purchase #7	$119.98	5.773%	$126.9064	$126.91	$126.90	$126.90
7 purchase totals =	$905.56		$967.2441	$967.24	$967.25	$967.20