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	$158.93	6.226%	$168.825	$168.83	$168.85	$168.80
Purchase #2	$227.67	4.798%	$238.5936	$238.59	$238.60	$238.60
Purchase #3	$192.63	3.530%	$199.4298	$199.43	$199.45	$199.40
Purchase #4	$132.43	10.111%	$145.82	$145.82	$145.80	$145.80
Purchase #5	$187.78	9.516%	$205.6491	$205.65	$205.65	$205.60
Purchase #6	$48.27	9.571%	$52.8899	$52.89	$52.90	$52.90
Purchase #7	$246.43	7.362%	$264.5722	$264.57	$264.55	$264.60
7 purchase totals =	$1,194.14		$1,275.7796	$1,275.78	$1,275.80	$1,275.70