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	$201.90	10.398%	$222.8936	$222.89	$222.90	$222.90
Purchase #2	$195.27	6.795%	$208.5386	$208.54	$208.55	$208.50
Purchase #3	$247.72	5.450%	$261.2207	$261.22	$261.20	$261.20
Purchase #4	$46.25	7.392%	$49.6688	$49.67	$49.65	$49.70
Purchase #5	$211.40	3.721%	$219.2662	$219.27	$219.25	$219.30
Purchase #6	$95.92	8.147%	$103.7346	$103.73	$103.75	$103.70
Purchase #7	$40.85	5.608%	$43.1409	$43.14	$43.15	$43.10
7 purchase totals =	$1,039.31		$1,108.4634	$1,108.46	$1,108.45	$1,108.40