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	$56.78	7.331%	$60.9425	$60.94	$60.95	$60.90
Purchase #2	$153.80	13.391%	$174.3954	$174.40	$174.40	$174.40
Purchase #3	$167.72	6.310%	$178.3031	$178.30	$178.30	$178.30
Purchase #4	$66.26	9.414%	$72.4977	$72.50	$72.50	$72.50
Purchase #5	$185.86	4.591%	$194.3928	$194.39	$194.40	$194.40
Purchase #6	$43.96	3.868%	$45.6604	$45.66	$45.65	$45.70
Purchase #7	$213.40	3.584%	$221.0483	$221.05	$221.05	$221.00
7 purchase totals =	$887.78		$947.2402	$947.24	$947.25	$947.20