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	$93.88	9.280%	$102.5921	$102.59	$102.60	$102.60
Purchase #2	$121.96	13.834%	$138.8319	$138.83	$138.85	$138.80
Purchase #3	$128.50	13.542%	$145.9015	$145.90	$145.90	$145.90
Purchase #4	$248.73	3.159%	$256.5874	$256.59	$256.60	$256.60
Purchase #5	$108.66	4.849%	$113.9289	$113.93	$113.95	$113.90
Purchase #6	$119.66	6.593%	$127.5492	$127.55	$127.55	$127.50
Purchase #7	$172.50	13.650%	$196.0463	$196.05	$196.05	$196.00
7 purchase totals =	$993.89		$1,081.4373	$1,081.44	$1,081.50	$1,081.30