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	$176.44	10.264%	$194.5498	$194.55	$194.55	$194.50
Purchase #2	$25.60	8.741%	$27.8377	$27.84	$27.85	$27.80
Purchase #3	$110.88	3.758%	$115.0469	$115.05	$115.05	$115.00
Purchase #4	$52.37	7.176%	$56.1281	$56.13	$56.15	$56.10
Purchase #5	$37.76	13.850%	$42.9898	$42.99	$43.00	$43.00
Purchase #6	$200.96	4.217%	$209.4345	$209.43	$209.45	$209.40
Purchase #7	$20.26	5.339%	$21.3417	$21.34	$21.35	$21.30
7 purchase totals =	$624.27		$667.3285	$667.33	$667.40	$667.10