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	$103.53	8.486%	$112.3156	$112.32	$112.30	$112.30
Purchase #2	$218.78	5.172%	$230.0953	$230.10	$230.10	$230.10
Purchase #3	$72.76	3.674%	$75.4332	$75.43	$75.45	$75.40
Purchase #4	$93.76	7.620%	$100.9045	$100.90	$100.90	$100.90
Purchase #5	$99.30	5.570%	$104.831	$104.83	$104.85	$104.80
Purchase #6	$125.32	10.779%	$138.8282	$138.83	$138.85	$138.80
Purchase #7	$232.53	4.320%	$242.5753	$242.58	$242.60	$242.60
7 purchase totals =	$945.98		$1,004.9831	$1,004.99	$1,005.05	$1,004.90