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	$92.89	12.857%	$104.8329	$104.83	$104.85	$104.80
Purchase #2	$189.83	3.731%	$196.9126	$196.91	$196.90	$196.90
Purchase #3	$40.35	5.141%	$42.4244	$42.42	$42.40	$42.40
Purchase #4	$224.40	7.620%	$241.4993	$241.50	$241.50	$241.50
Purchase #5	$115.71	9.209%	$126.3657	$126.37	$126.35	$126.40
Purchase #6	$144.50	5.367%	$152.2553	$152.26	$152.25	$152.30
Purchase #7	$189.54	11.114%	$210.6055	$210.61	$210.60	$210.60
7 purchase totals =	$997.22		$1,074.8957	$1,074.90	$1,074.85	$1,074.90