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	$56.44	9.351%	$61.7177	$61.72	$61.70	$61.70
Purchase #2	$152.91	10.452%	$168.8922	$168.89	$168.90	$168.90
Purchase #3	$153.94	6.538%	$164.0046	$164.00	$164.00	$164.00
Purchase #4	$23.58	8.271%	$25.5303	$25.53	$25.55	$25.50
Purchase #5	$12.33	5.831%	$13.049	$13.05	$13.05	$13.00
Purchase #6	$54.47	5.422%	$57.4234	$57.42	$57.40	$57.40
Purchase #7	$56.52	8.789%	$61.4875	$61.49	$61.50	$61.50
7 purchase totals =	$510.19		$552.1047	$552.10	$552.10	$552.00