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	$195.49	11.751%	$218.462	$218.46	$218.45	$218.50
Purchase #2	$170.44	6.377%	$181.309	$181.31	$181.30	$181.30
Purchase #3	$184.47	6.492%	$196.4458	$196.45	$196.45	$196.40
Purchase #4	$106.82	4.577%	$111.7092	$111.71	$111.70	$111.70
Purchase #5	$214.90	4.475%	$224.5168	$224.52	$224.50	$224.50
Purchase #6	$218.90	5.797%	$231.5896	$231.59	$231.60	$231.60
Purchase #7	$67.38	6.157%	$71.5286	$71.53	$71.55	$71.50
7 purchase totals =	$1,158.40		$1,235.5610	$1,235.57	$1,235.55	$1,235.50