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	$38.29	12.551%	$43.0958	$43.10	$43.10	$43.10
Purchase #2	$39.71	9.604%	$43.5237	$43.52	$43.50	$43.50
Purchase #3	$75.48	13.363%	$85.5664	$85.57	$85.55	$85.60
Purchase #4	$135.54	9.574%	$148.5166	$148.52	$148.50	$148.50
Purchase #5	$226.71	5.200%	$238.4989	$238.50	$238.50	$238.50
Purchase #6	$181.95	11.271%	$202.4576	$202.46	$202.45	$202.50
Purchase #7	$87.49	4.509%	$91.4349	$91.43	$91.45	$91.40
7 purchase totals =	$785.17		$853.0939	$853.10	$853.05	$853.10