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	$45.79	13.533%	$51.9868	$51.99	$52.00	$52.00
Purchase #2	$111.32	11.293%	$123.8914	$123.89	$123.90	$123.90
Purchase #3	$36.77	10.280%	$40.55	$40.55	$40.55	$40.60
Purchase #4	$54.65	11.759%	$61.0763	$61.08	$61.10	$61.10
Purchase #5	$88.86	3.632%	$92.0874	$92.09	$92.10	$92.10
Purchase #6	$164.93	12.817%	$186.0691	$186.07	$186.05	$186.10
Purchase #7	$6.61	10.380%	$7.2961	$7.30	$7.30	$7.30
7 purchase totals =	$508.93		$562.9571	$562.97	$563.00	$563.10