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	$61.83	8.277%	$66.9477	$66.95	$66.95	$66.90
Purchase #2	$22.67	10.722%	$25.1007	$25.10	$25.10	$25.10
Purchase #3	$168.34	3.687%	$174.5467	$174.55	$174.55	$174.50
Purchase #4	$45.50	12.564%	$51.2166	$51.22	$51.20	$51.20
Purchase #5	$62.56	13.842%	$71.2196	$71.22	$71.20	$71.20
Purchase #6	$117.96	9.492%	$129.1568	$129.16	$129.15	$129.20
Purchase #7	$145.70	4.638%	$152.4576	$152.46	$152.45	$152.50
7 purchase totals =	$624.56		$670.6457	$670.66	$670.60	$670.60