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	$57.41	3.805%	$59.5945	$59.59	$59.60	$59.60
Purchase #2	$25.92	6.194%	$27.5255	$27.53	$27.55	$27.50
Purchase #3	$116.99	9.294%	$127.8631	$127.86	$127.85	$127.90
Purchase #4	$122.50	8.805%	$133.2861	$133.29	$133.30	$133.30
Purchase #5	$223.80	3.386%	$231.3779	$231.38	$231.40	$231.40
Purchase #6	$75.72	12.578%	$85.2441	$85.24	$85.25	$85.20
Purchase #7	$181.35	11.129%	$201.5324	$201.53	$201.55	$201.50
7 purchase totals =	$803.69		$866.4236	$866.42	$866.50	$866.40