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	$143.61	13.416%	$162.8767	$162.88	$162.90	$162.90
Purchase #2	$31.96	6.838%	$34.1454	$34.15	$34.15	$34.10
Purchase #3	$164.36	6.449%	$174.9596	$174.96	$174.95	$175.00
Purchase #4	$141.33	8.438%	$153.2554	$153.26	$153.25	$153.30
Purchase #5	$32.32	5.587%	$34.1257	$34.13	$34.15	$34.10
Purchase #6	$104.80	6.319%	$111.4223	$111.42	$111.40	$111.40
Purchase #7	$5.77	5.795%	$6.1044	$6.10	$6.10	$6.10
7 purchase totals =	$624.15		$676.8895	$676.90	$676.90	$676.90