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	$14.78	4.628%	$15.464	$15.46	$15.45	$15.50
Purchase #2	$186.48	11.250%	$207.459	$207.46	$207.45	$207.50
Purchase #3	$173.93	6.721%	$185.6198	$185.62	$185.60	$185.60
Purchase #4	$95.46	8.443%	$103.5197	$103.52	$103.50	$103.50
Purchase #5	$170.47	3.762%	$176.8831	$176.88	$176.90	$176.90
Purchase #6	$181.25	13.400%	$205.5375	$205.54	$205.55	$205.50
Purchase #7	$129.63	13.606%	$147.2675	$147.27	$147.25	$147.30
7 purchase totals =	$952.00		$1,041.7506	$1,041.75	$1,041.70	$1,041.80