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	$40.52	13.670%	$46.0591	$46.06	$46.05	$46.10
Purchase #2	$55.32	8.336%	$59.9315	$59.93	$59.95	$59.90
Purchase #3	$155.95	12.412%	$175.3065	$175.31	$175.30	$175.30
Purchase #4	$191.84	8.435%	$208.0217	$208.02	$208.00	$208.00
Purchase #5	$40.31	6.729%	$43.0225	$43.02	$43.00	$43.00
Purchase #6	$148.72	4.215%	$154.9885	$154.99	$155.00	$155.00
Purchase #7	$48.38	4.490%	$50.5523	$50.55	$50.55	$50.60
7 purchase totals =	$681.04		$737.8821	$737.88	$737.85	$737.90