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	$166.72	11.805%	$186.4013	$186.40	$186.40	$186.40
Purchase #2	$196.78	8.484%	$213.4748	$213.47	$213.45	$213.50
Purchase #3	$204.53	5.196%	$215.1574	$215.16	$215.15	$215.20
Purchase #4	$141.86	12.698%	$159.8734	$159.87	$159.85	$159.90
Purchase #5	$47.38	11.773%	$52.958	$52.96	$52.95	$53.00
Purchase #6	$222.96	6.691%	$237.8783	$237.88	$237.90	$237.90
Purchase #7	$42.54	9.426%	$46.5498	$46.55	$46.55	$46.50
7 purchase totals =	$1,022.77		$1,112.2930	$1,112.29	$1,112.25	$1,112.40