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	$200.55	10.842%	$222.2936	$222.29	$222.30	$222.30
Purchase #2	$32.77	4.663%	$34.2981	$34.30	$34.30	$34.30
Purchase #3	$170.92	6.515%	$182.0554	$182.06	$182.05	$182.10
Purchase #4	$133.38	10.509%	$147.3969	$147.40	$147.40	$147.40
Purchase #5	$86.50	4.573%	$90.4556	$90.46	$90.45	$90.50
Purchase #6	$45.89	7.657%	$49.4038	$49.40	$49.40	$49.40
Purchase #7	$207.36	5.618%	$219.0095	$219.01	$219.00	$219.00
7 purchase totals =	$877.37		$944.9129	$944.92	$944.90	$945.00