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	$104.83	6.869%	$112.0308	$112.03	$112.05	$112.00
Purchase #2	$41.32	5.358%	$43.5339	$43.53	$43.55	$43.50
Purchase #3	$164.46	4.723%	$172.2274	$172.23	$172.25	$172.20
Purchase #4	$70.29	7.156%	$75.32	$75.32	$75.30	$75.30
Purchase #5	$56.64	6.825%	$60.5057	$60.51	$60.50	$60.50
Purchase #6	$205.63	11.788%	$229.8697	$229.87	$229.85	$229.90
Purchase #7	$44.76	3.800%	$46.4609	$46.46	$46.45	$46.50
7 purchase totals =	$687.93		$739.9484	$739.95	$739.95	$739.90