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	$191.79	11.610%	$214.0568	$214.06	$214.05	$214.10
Purchase #2	$42.39	3.344%	$43.8075	$43.81	$43.80	$43.80
Purchase #3	$198.36	13.792%	$225.7178	$225.72	$225.70	$225.70
Purchase #4	$70.42	3.152%	$72.6396	$72.64	$72.65	$72.60
Purchase #5	$222.71	6.145%	$236.3955	$236.40	$236.40	$236.40
Purchase #6	$109.67	5.570%	$115.7786	$115.78	$115.80	$115.80
Purchase #7	$225.92	6.262%	$240.0671	$240.07	$240.05	$240.10
7 purchase totals =	$1,061.26		$1,148.4629	$1,148.48	$1,148.45	$1,148.50