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	$72.30	4.522%	$75.5694	$75.57	$75.55	$75.60
Purchase #2	$75.72	8.523%	$82.1736	$82.17	$82.15	$82.20
Purchase #3	$11.30	13.870%	$12.8673	$12.87	$12.85	$12.90
Purchase #4	$198.75	5.193%	$209.0711	$209.07	$209.05	$209.10
Purchase #5	$12.63	5.332%	$13.3034	$13.30	$13.30	$13.30
Purchase #6	$166.30	8.175%	$179.895	$179.90	$179.90	$179.90
Purchase #7	$178.71	3.750%	$185.4116	$185.41	$185.40	$185.40
7 purchase totals =	$715.71		$758.2914	$758.29	$758.20	$758.40