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	$63.83	12.593%	$71.8681	$71.87	$71.85	$71.90
Purchase #2	$162.35	6.136%	$172.3118	$172.31	$172.30	$172.30
Purchase #3	$243.69	6.523%	$259.5859	$259.59	$259.60	$259.60
Purchase #4	$57.62	9.472%	$63.0778	$63.08	$63.10	$63.10
Purchase #5	$52.25	13.830%	$59.4762	$59.48	$59.50	$59.50
Purchase #6	$176.60	12.146%	$198.0498	$198.05	$198.05	$198.00
Purchase #7	$31.51	9.707%	$34.5687	$34.57	$34.55	$34.60
7 purchase totals =	$787.85		$858.9383	$858.95	$858.95	$859.00