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	$225.32	11.154%	$250.4522	$250.45	$250.45	$250.50
Purchase #2	$18.87	5.592%	$19.9252	$19.93	$19.95	$19.90
Purchase #3	$24.43	12.364%	$27.4505	$27.45	$27.45	$27.50
Purchase #4	$13.59	6.371%	$14.4558	$14.46	$14.45	$14.50
Purchase #5	$78.53	3.465%	$81.2511	$81.25	$81.25	$81.30
Purchase #6	$172.54	7.417%	$185.3373	$185.34	$185.35	$185.30
Purchase #7	$158.84	11.372%	$176.9033	$176.90	$176.90	$176.90
7 purchase totals =	$692.12		$755.7754	$755.78	$755.80	$755.90