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	$81.57	4.828%	$85.5082	$85.51	$85.50	$85.50
Purchase #2	$138.55	5.137%	$145.6673	$145.67	$145.65	$145.70
Purchase #3	$23.91	6.566%	$25.4799	$25.48	$25.50	$25.50
Purchase #4	$193.65	3.658%	$200.7337	$200.73	$200.75	$200.70
Purchase #5	$181.43	13.140%	$205.2699	$205.27	$205.25	$205.30
Purchase #6	$66.51	6.226%	$70.6509	$70.65	$70.65	$70.70
Purchase #7	$81.88	9.278%	$89.4768	$89.48	$89.50	$89.50
7 purchase totals =	$767.50		$822.7867	$822.79	$822.80	$822.90