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	$37.92	10.177%	$41.7791	$41.78	$41.80	$41.80
Purchase #2	$111.36	6.125%	$118.1808	$118.18	$118.20	$118.20
Purchase #3	$115.63	8.564%	$125.5326	$125.53	$125.55	$125.50
Purchase #4	$241.93	3.535%	$250.4822	$250.48	$250.50	$250.50
Purchase #5	$142.66	6.556%	$152.0128	$152.01	$152.00	$152.00
Purchase #6	$175.36	12.267%	$196.8714	$196.87	$196.85	$196.90
Purchase #7	$160.76	9.848%	$176.5916	$176.59	$176.60	$176.60
7 purchase totals =	$985.62		$1,061.4505	$1,061.44	$1,061.50	$1,061.50