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	$180.25	13.180%	$204.007	$204.01	$204.00	$204.00
Purchase #2	$102.26	10.633%	$113.1333	$113.13	$113.15	$113.10
Purchase #3	$20.69	10.202%	$22.8008	$22.80	$22.80	$22.80
Purchase #4	$194.72	8.264%	$210.8117	$210.81	$210.80	$210.80
Purchase #5	$141.45	9.513%	$154.9061	$154.91	$154.90	$154.90
Purchase #6	$187.82	4.556%	$196.3771	$196.38	$196.40	$196.40
Purchase #7	$154.91	6.839%	$165.5043	$165.50	$165.50	$165.50
7 purchase totals =	$982.10		$1,067.5403	$1,067.54	$1,067.55	$1,067.50