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	$211.78	9.354%	$231.5899	$231.59	$231.60	$231.60
Purchase #2	$36.61	11.800%	$40.93	$40.93	$40.95	$40.90
Purchase #3	$6.48	8.760%	$7.0476	$7.05	$7.05	$7.00
Purchase #4	$201.58	5.826%	$213.3241	$213.32	$213.30	$213.30
Purchase #5	$91.32	10.527%	$100.9333	$100.93	$100.95	$100.90
Purchase #6	$185.37	7.586%	$199.4322	$199.43	$199.45	$199.40
Purchase #7	$108.96	4.762%	$114.1487	$114.15	$114.15	$114.10
7 purchase totals =	$842.10		$907.4058	$907.40	$907.45	$907.20