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	$95.55	10.119%	$105.2187	$105.22	$105.20	$105.20
Purchase #2	$107.75	7.228%	$115.5382	$115.54	$115.55	$115.50
Purchase #3	$185.57	4.582%	$194.0728	$194.07	$194.05	$194.10
Purchase #4	$228.76	9.105%	$249.5886	$249.59	$249.60	$249.60
Purchase #5	$218.81	4.593%	$228.8599	$228.86	$228.85	$228.90
Purchase #6	$147.61	3.722%	$153.104	$153.10	$153.10	$153.10
Purchase #7	$27.77	11.822%	$31.053	$31.05	$31.05	$31.10
7 purchase totals =	$1,011.82		$1,077.4352	$1,077.43	$1,077.40	$1,077.50