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	$250.89	13.761%	$285.415	$285.42	$285.40	$285.40
Purchase #2	$187.43	12.315%	$210.512	$210.51	$210.50	$210.50
Purchase #3	$150.29	7.217%	$161.1364	$161.14	$161.15	$161.10
Purchase #4	$106.49	6.177%	$113.0679	$113.07	$113.05	$113.10
Purchase #5	$56.33	5.620%	$59.4957	$59.50	$59.50	$59.50
Purchase #6	$155.25	4.241%	$161.8342	$161.83	$161.85	$161.80
Purchase #7	$184.88	3.752%	$191.8167	$191.82	$191.80	$191.80
7 purchase totals =	$1,091.56		$1,183.2779	$1,183.29	$1,183.25	$1,183.20