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	$248.63	4.279%	$259.2689	$259.27	$259.25	$259.30
Purchase #2	$151.56	10.424%	$167.3586	$167.36	$167.35	$167.40
Purchase #3	$192.33	4.113%	$200.2405	$200.24	$200.25	$200.20
Purchase #4	$100.93	12.498%	$113.5442	$113.54	$113.55	$113.50
Purchase #5	$150.65	9.337%	$164.7162	$164.72	$164.70	$164.70
Purchase #6	$217.82	7.565%	$234.2981	$234.30	$234.30	$234.30
Purchase #7	$101.66	9.677%	$111.4976	$111.50	$111.50	$111.50
7 purchase totals =	$1,163.58		$1,250.9241	$1,250.93	$1,250.90	$1,250.90