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	$45.86	8.765%	$49.8796	$49.88	$49.90	$49.90
Purchase #2	$203.94	11.563%	$227.5216	$227.52	$227.50	$227.50
Purchase #3	$214.69	7.750%	$231.3285	$231.33	$231.35	$231.30
Purchase #4	$71.33	13.191%	$80.7391	$80.74	$80.75	$80.70
Purchase #5	$218.34	4.795%	$228.8094	$228.81	$228.80	$228.80
Purchase #6	$111.51	10.812%	$123.5665	$123.57	$123.55	$123.60
Purchase #7	$159.55	4.427%	$166.6133	$166.61	$166.60	$166.60
7 purchase totals =	$1,025.22		$1,108.4580	$1,108.46	$1,108.45	$1,108.40