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	$181.34	8.442%	$196.6487	$196.65	$196.65	$196.60
Purchase #2	$46.88	7.638%	$50.4607	$50.46	$50.45	$50.50
Purchase #3	$81.89	6.417%	$87.1449	$87.14	$87.15	$87.10
Purchase #4	$105.87	8.597%	$114.9716	$114.97	$114.95	$115.00
Purchase #5	$56.91	4.569%	$59.5102	$59.51	$59.50	$59.50
Purchase #6	$228.50	12.738%	$257.6063	$257.61	$257.60	$257.60
Purchase #7	$121.63	10.286%	$134.1409	$134.14	$134.15	$134.10
7 purchase totals =	$823.02		$900.4833	$900.48	$900.45	$900.40