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	$223.53	12.357%	$251.1516	$251.15	$251.15	$251.20
Purchase #2	$167.55	6.848%	$179.0238	$179.02	$179.00	$179.00
Purchase #3	$232.69	11.678%	$259.8635	$259.86	$259.85	$259.90
Purchase #4	$198.92	6.323%	$211.4977	$211.50	$211.50	$211.50
Purchase #5	$76.60	7.528%	$82.3664	$82.37	$82.35	$82.40
Purchase #6	$112.89	9.103%	$123.1664	$123.17	$123.15	$123.20
Purchase #7	$100.49	11.633%	$112.18	$112.18	$112.20	$112.20
7 purchase totals =	$1,112.67		$1,219.2494	$1,219.25	$1,219.20	$1,219.40