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	$48.48	12.696%	$54.635	$54.64	$54.65	$54.60
Purchase #2	$112.96	13.850%	$128.605	$128.61	$128.60	$128.60
Purchase #3	$42.66	3.410%	$44.1147	$44.11	$44.10	$44.10
Purchase #4	$67.37	6.782%	$71.939	$71.94	$71.95	$71.90
Purchase #5	$38.93	7.770%	$41.9549	$41.95	$41.95	$42.00
Purchase #6	$87.63	4.143%	$91.2605	$91.26	$91.25	$91.30
Purchase #7	$117.78	13.836%	$134.076	$134.08	$134.10	$134.10
7 purchase totals =	$515.81		$566.5851	$566.59	$566.60	$566.60