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	$53.26	10.577%	$58.8933	$58.89	$58.90	$58.90
Purchase #2	$150.69	4.540%	$157.5313	$157.53	$157.55	$157.50
Purchase #3	$141.75	8.352%	$153.589	$153.59	$153.60	$153.60
Purchase #4	$130.52	10.144%	$143.7599	$143.76	$143.75	$143.80
Purchase #5	$206.48	8.787%	$224.6234	$224.62	$224.60	$224.60
Purchase #6	$217.74	9.349%	$238.0965	$238.10	$238.10	$238.10
Purchase #7	$40.78	5.163%	$42.8855	$42.89	$42.90	$42.90
7 purchase totals =	$941.22		$1,019.3789	$1,019.38	$1,019.40	$1,019.40