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	$211.93	10.123%	$233.3837	$233.38	$233.40	$233.40
Purchase #2	$151.68	8.354%	$164.3513	$164.35	$164.35	$164.40
Purchase #3	$153.59	9.733%	$168.5389	$168.54	$168.55	$168.50
Purchase #4	$54.93	12.351%	$61.7144	$61.71	$61.70	$61.70
Purchase #5	$87.30	4.849%	$91.5332	$91.53	$91.55	$91.50
Purchase #6	$237.49	5.865%	$251.4188	$251.42	$251.40	$251.40
Purchase #7	$198.52	11.859%	$222.0625	$222.06	$222.05	$222.10
7 purchase totals =	$1,095.44		$1,193.0028	$1,192.99	$1,193.00	$1,193.00