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	$38.78	11.549%	$43.2587	$43.26	$43.25	$43.30
Purchase #2	$96.26	3.412%	$99.5444	$99.54	$99.55	$99.50
Purchase #3	$220.83	8.805%	$240.2741	$240.27	$240.25	$240.30
Purchase #4	$174.96	6.776%	$186.8153	$186.82	$186.80	$186.80
Purchase #5	$214.58	4.206%	$223.6052	$223.61	$223.60	$223.60
Purchase #6	$62.81	5.144%	$66.0409	$66.04	$66.05	$66.00
Purchase #7	$156.65	12.598%	$176.3848	$176.38	$176.40	$176.40
7 purchase totals =	$964.87		$1,035.9234	$1,035.92	$1,035.90	$1,035.90