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	$112.84	4.343%	$117.7406	$117.74	$117.75	$117.70
Purchase #2	$244.99	6.458%	$260.8115	$260.81	$260.80	$260.80
Purchase #3	$145.83	3.864%	$151.4649	$151.46	$151.45	$151.50
Purchase #4	$102.42	13.861%	$116.6164	$116.62	$116.60	$116.60
Purchase #5	$119.28	6.641%	$127.2014	$127.20	$127.20	$127.20
Purchase #6	$240.75	6.436%	$256.2447	$256.24	$256.25	$256.20
Purchase #7	$112.48	7.357%	$120.7552	$120.76	$120.75	$120.80
7 purchase totals =	$1,078.59		$1,150.8347	$1,150.83	$1,150.80	$1,150.80