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	$227.63	6.146%	$241.6201	$241.62	$241.60	$241.60
Purchase #2	$186.36	6.275%	$198.0541	$198.05	$198.05	$198.10
Purchase #3	$46.31	9.814%	$50.8549	$50.85	$50.85	$50.90
Purchase #4	$77.86	5.458%	$82.1096	$82.11	$82.10	$82.10
Purchase #5	$180.58	7.484%	$194.0946	$194.09	$194.10	$194.10
Purchase #6	$97.47	3.542%	$100.9224	$100.92	$100.90	$100.90
Purchase #7	$186.86	6.647%	$199.2806	$199.28	$199.30	$199.30
7 purchase totals =	$1,003.07		$1,066.9363	$1,066.92	$1,066.90	$1,067.00