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	$123.91	3.185%	$127.8565	$127.86	$127.85	$127.90
Purchase #2	$15.29	6.554%	$16.2921	$16.29	$16.30	$16.30
Purchase #3	$123.40	13.677%	$140.2774	$140.28	$140.30	$140.30
Purchase #4	$245.28	9.797%	$269.3101	$269.31	$269.30	$269.30
Purchase #5	$160.82	13.871%	$183.1273	$183.13	$183.15	$183.10
Purchase #6	$250.78	13.348%	$284.2541	$284.25	$284.25	$284.30
Purchase #7	$92.71	10.120%	$102.0923	$102.09	$102.10	$102.10
7 purchase totals =	$1,012.19		$1,123.2098	$1,123.21	$1,123.25	$1,123.30