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	$204.50	6.392%	$217.5716	$217.57	$217.55	$217.60
Purchase #2	$187.78	13.115%	$212.4073	$212.41	$212.40	$212.40
Purchase #3	$102.31	13.823%	$116.4523	$116.45	$116.45	$116.50
Purchase #4	$96.89	6.622%	$103.3061	$103.31	$103.30	$103.30
Purchase #5	$68.63	3.588%	$71.0924	$71.09	$71.10	$71.10
Purchase #6	$104.56	4.685%	$109.4586	$109.46	$109.45	$109.50
Purchase #7	$205.88	9.460%	$225.3562	$225.36	$225.35	$225.40
7 purchase totals =	$970.55		$1,055.6445	$1,055.65	$1,055.60	$1,055.80