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	$162.61	9.595%	$178.2124	$178.21	$178.20	$178.20
Purchase #2	$94.43	6.238%	$100.3205	$100.32	$100.30	$100.30
Purchase #3	$236.54	9.402%	$258.7795	$258.78	$258.80	$258.80
Purchase #4	$138.31	9.852%	$151.9363	$151.94	$151.95	$151.90
Purchase #5	$45.31	6.731%	$48.3598	$48.36	$48.35	$48.40
Purchase #6	$129.46	7.417%	$139.062	$139.06	$139.05	$139.10
Purchase #7	$157.50	13.819%	$179.2649	$179.26	$179.25	$179.30
7 purchase totals =	$964.16		$1,055.9354	$1,055.93	$1,055.90	$1,056.00