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	$23.51	8.213%	$25.4409	$25.44	$25.45	$25.40
Purchase #2	$250.66	12.118%	$281.035	$281.04	$281.05	$281.00
Purchase #3	$149.78	8.344%	$162.2776	$162.28	$162.30	$162.30
Purchase #4	$62.33	7.546%	$67.0334	$67.03	$67.05	$67.00
Purchase #5	$196.94	10.452%	$217.5242	$217.52	$217.50	$217.50
Purchase #6	$99.57	5.591%	$105.137	$105.14	$105.15	$105.10
Purchase #7	$11.65	3.743%	$12.0861	$12.09	$12.10	$12.10
7 purchase totals =	$794.44		$870.5342	$870.54	$870.60	$870.40