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	$70.52	3.711%	$73.137	$73.14	$73.15	$73.10
Purchase #2	$214.44	10.418%	$236.7804	$236.78	$236.80	$236.80
Purchase #3	$38.97	11.486%	$43.4461	$43.45	$43.45	$43.40
Purchase #4	$178.77	12.214%	$200.605	$200.61	$200.60	$200.60
Purchase #5	$138.61	5.716%	$146.5329	$146.53	$146.55	$146.50
Purchase #6	$229.96	8.850%	$250.3115	$250.31	$250.30	$250.30
Purchase #7	$50.40	12.651%	$56.7761	$56.78	$56.80	$56.80
7 purchase totals =	$921.67		$1,007.5890	$1,007.60	$1,007.65	$1,007.50