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	$144.96	13.497%	$164.5253	$164.53	$164.55	$164.50
Purchase #2	$200.81	3.580%	$207.999	$208.00	$208.00	$208.00
Purchase #3	$143.65	5.474%	$151.5134	$151.51	$151.50	$151.50
Purchase #4	$152.55	13.687%	$173.4295	$173.43	$173.45	$173.40
Purchase #5	$207.89	11.627%	$232.0614	$232.06	$232.05	$232.10
Purchase #6	$59.30	4.803%	$62.1482	$62.15	$62.15	$62.10
Purchase #7	$188.71	10.145%	$207.8546	$207.85	$207.85	$207.90
7 purchase totals =	$1,097.87		$1,199.5314	$1,199.53	$1,199.55	$1,199.50