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	$236.51	10.684%	$261.7787	$261.78	$261.80	$261.80
Purchase #2	$238.67	8.736%	$259.5202	$259.52	$259.50	$259.50
Purchase #3	$40.39	12.233%	$45.3309	$45.33	$45.35	$45.30
Purchase #4	$40.93	3.745%	$42.4628	$42.46	$42.45	$42.50
Purchase #5	$249.88	12.604%	$281.3749	$281.37	$281.35	$281.40
Purchase #6	$46.66	9.608%	$51.1431	$51.14	$51.15	$51.10
Purchase #7	$121.79	3.857%	$126.4874	$126.49	$126.50	$126.50
7 purchase totals =	$974.83		$1,068.0980	$1,068.09	$1,068.10	$1,068.10