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	$138.96	3.450%	$143.7541	$143.75	$143.75	$143.80
Purchase #2	$46.39	4.441%	$48.4502	$48.45	$48.45	$48.50
Purchase #3	$59.81	9.299%	$65.3717	$65.37	$65.35	$65.40
Purchase #4	$130.73	6.714%	$139.5072	$139.51	$139.50	$139.50
Purchase #5	$87.36	3.845%	$90.719	$90.72	$90.70	$90.70
Purchase #6	$108.62	9.109%	$118.5142	$118.51	$118.50	$118.50
Purchase #7	$89.39	9.117%	$97.5397	$97.54	$97.55	$97.50
7 purchase totals =	$661.26		$703.8561	$703.85	$703.80	$703.90