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	$171.40	5.756%	$181.2658	$181.27	$181.25	$181.30
Purchase #2	$77.34	12.432%	$86.9549	$86.95	$86.95	$87.00
Purchase #3	$65.55	10.451%	$72.4006	$72.40	$72.40	$72.40
Purchase #4	$246.63	13.401%	$279.6809	$279.68	$279.70	$279.70
Purchase #5	$75.83	8.364%	$82.1724	$82.17	$82.15	$82.20
Purchase #6	$173.33	13.513%	$196.7521	$196.75	$196.75	$196.80
Purchase #7	$205.35	8.855%	$223.5337	$223.53	$223.55	$223.50
7 purchase totals =	$1,015.43		$1,122.7604	$1,122.75	$1,122.75	$1,122.90