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	$101.57	8.423%	$110.1252	$110.13	$110.15	$110.10
Purchase #2	$248.32	12.714%	$279.8914	$279.89	$279.90	$279.90
Purchase #3	$12.33	12.667%	$13.8918	$13.89	$13.90	$13.90
Purchase #4	$164.93	8.326%	$178.6621	$178.66	$178.65	$178.70
Purchase #5	$98.37	4.773%	$103.0652	$103.07	$103.05	$103.10
Purchase #6	$6.74	5.409%	$7.1046	$7.10	$7.10	$7.10
Purchase #7	$39.35	9.684%	$43.1607	$43.16	$43.15	$43.20
7 purchase totals =	$671.61		$735.9010	$735.90	$735.90	$736.00