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	$87.69	3.359%	$90.6355	$90.64	$90.65	$90.60
Purchase #2	$11.87	9.736%	$13.0257	$13.03	$13.05	$13.00
Purchase #3	$192.69	7.279%	$206.7159	$206.72	$206.70	$206.70
Purchase #4	$40.49	6.537%	$43.1368	$43.14	$43.15	$43.10
Purchase #5	$146.83	3.145%	$151.4478	$151.45	$151.45	$151.40
Purchase #6	$225.51	3.706%	$233.8674	$233.87	$233.85	$233.90
Purchase #7	$73.47	5.729%	$77.6791	$77.68	$77.70	$77.70
7 purchase totals =	$778.55		$816.5082	$816.53	$816.55	$816.40