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	$98.83	9.743%	$108.459	$108.46	$108.45	$108.50
Purchase #2	$169.29	12.750%	$190.8745	$190.87	$190.85	$190.90
Purchase #3	$207.39	13.480%	$235.3462	$235.35	$235.35	$235.30
Purchase #4	$125.54	9.280%	$137.1901	$137.19	$137.20	$137.20
Purchase #5	$159.45	4.338%	$166.3669	$166.37	$166.35	$166.40
Purchase #6	$48.80	13.167%	$55.2255	$55.23	$55.25	$55.20
Purchase #7	$145.42	3.413%	$150.3832	$150.38	$150.40	$150.40
7 purchase totals =	$954.72		$1,043.8454	$1,043.85	$1,043.85	$1,043.90