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	$38.87	4.437%	$40.5947	$40.59	$40.60	$40.60
Purchase #2	$158.57	6.342%	$168.6265	$168.63	$168.65	$168.60
Purchase #3	$212.67	9.613%	$233.114	$233.11	$233.10	$233.10
Purchase #4	$79.76	9.475%	$87.3173	$87.32	$87.30	$87.30
Purchase #5	$227.52	4.673%	$238.152	$238.15	$238.15	$238.20
Purchase #6	$248.25	3.822%	$257.7381	$257.74	$257.75	$257.70
Purchase #7	$134.72	3.288%	$139.1496	$139.15	$139.15	$139.10
7 purchase totals =	$1,100.36		$1,164.6922	$1,164.69	$1,164.70	$1,164.60