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	$61.33	6.108%	$65.076	$65.08	$65.10	$65.10
Purchase #2	$136.79	3.418%	$141.4655	$141.47	$141.45	$141.50
Purchase #3	$231.96	10.594%	$256.5338	$256.53	$256.55	$256.50
Purchase #4	$208.38	7.158%	$223.2958	$223.30	$223.30	$223.30
Purchase #5	$223.40	4.820%	$234.1679	$234.17	$234.15	$234.20
Purchase #6	$115.76	9.239%	$126.4551	$126.46	$126.45	$126.50
Purchase #7	$119.71	11.847%	$133.892	$133.89	$133.90	$133.90
7 purchase totals =	$1,097.33		$1,180.8861	$1,180.90	$1,180.90	$1,181.00