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	$130.90	11.255%	$145.6328	$145.63	$145.65	$145.60
Purchase #2	$141.67	11.653%	$158.1788	$158.18	$158.20	$158.20
Purchase #3	$106.62	3.103%	$109.9284	$109.93	$109.95	$109.90
Purchase #4	$211.29	9.354%	$231.0541	$231.05	$231.05	$231.10
Purchase #5	$75.62	4.288%	$78.8626	$78.86	$78.85	$78.90
Purchase #6	$64.71	4.467%	$67.6006	$67.60	$67.60	$67.60
Purchase #7	$33.40	13.804%	$38.0105	$38.01	$38.00	$38.00
7 purchase totals =	$764.21		$829.2678	$829.26	$829.30	$829.30