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	$101.73	9.594%	$111.49	$111.49	$111.50	$111.50
Purchase #2	$226.94	4.214%	$236.5033	$236.50	$236.50	$236.50
Purchase #3	$163.58	13.147%	$185.0859	$185.09	$185.10	$185.10
Purchase #4	$186.62	5.594%	$197.0595	$197.06	$197.05	$197.10
Purchase #5	$164.49	6.566%	$175.2904	$175.29	$175.30	$175.30
Purchase #6	$114.53	12.392%	$128.7226	$128.72	$128.70	$128.70
Purchase #7	$105.57	10.183%	$116.3202	$116.32	$116.30	$116.30
7 purchase totals =	$1,063.46		$1,150.4719	$1,150.47	$1,150.45	$1,150.50