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	$147.78	5.871%	$156.4562	$156.46	$156.45	$156.50
Purchase #2	$142.71	9.287%	$155.9635	$155.96	$155.95	$156.00
Purchase #3	$208.95	6.371%	$222.2622	$222.26	$222.25	$222.30
Purchase #4	$44.94	4.666%	$47.0369	$47.04	$47.05	$47.00
Purchase #5	$107.29	7.118%	$114.9269	$114.93	$114.95	$114.90
Purchase #6	$248.46	4.160%	$258.7959	$258.80	$258.80	$258.80
Purchase #7	$123.64	5.770%	$130.774	$130.77	$130.75	$130.80
7 purchase totals =	$1,023.77		$1,086.2156	$1,086.22	$1,086.20	$1,086.30