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	$8.38	6.762%	$8.9467	$8.95	$8.95	$8.90
Purchase #2	$150.99	11.851%	$168.8838	$168.88	$168.90	$168.90
Purchase #3	$54.35	5.375%	$57.2713	$57.27	$57.25	$57.30
Purchase #4	$160.54	9.822%	$176.3082	$176.31	$176.30	$176.30
Purchase #5	$81.48	9.715%	$89.3958	$89.40	$89.40	$89.40
Purchase #6	$146.43	5.853%	$155.0005	$155.00	$155.00	$155.00
Purchase #7	$47.84	11.844%	$53.5062	$53.51	$53.50	$53.50
7 purchase totals =	$650.01		$709.3125	$709.32	$709.30	$709.30