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	$101.38	8.116%	$109.608	$109.61	$109.60	$109.60
Purchase #2	$89.35	9.630%	$97.9544	$97.95	$97.95	$98.00
Purchase #3	$133.37	5.855%	$141.1788	$141.18	$141.20	$141.20
Purchase #4	$224.69	3.196%	$231.8711	$231.87	$231.85	$231.90
Purchase #5	$44.48	4.407%	$46.4402	$46.44	$46.45	$46.40
Purchase #6	$57.80	6.127%	$61.3414	$61.34	$61.35	$61.30
Purchase #7	$70.92	11.248%	$78.8971	$78.90	$78.90	$78.90
7 purchase totals =	$721.99		$767.2910	$767.29	$767.30	$767.30