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	$238.54	9.482%	$261.1584	$261.16	$261.15	$261.20
Purchase #2	$73.31	4.444%	$76.5679	$76.57	$76.55	$76.60
Purchase #3	$36.33	11.781%	$40.61	$40.61	$40.60	$40.60
Purchase #4	$239.86	10.678%	$265.4723	$265.47	$265.45	$265.50
Purchase #5	$47.93	5.870%	$50.7435	$50.74	$50.75	$50.70
Purchase #6	$51.25	11.418%	$57.1017	$57.10	$57.10	$57.10
Purchase #7	$51.37	5.526%	$54.2087	$54.21	$54.20	$54.20
7 purchase totals =	$738.59		$805.8625	$805.86	$805.80	$805.90