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	$207.40	3.793%	$215.2667	$215.27	$215.25	$215.30
Purchase #2	$192.32	10.561%	$212.6309	$212.63	$212.65	$212.60
Purchase #3	$223.54	6.534%	$238.1461	$238.15	$238.15	$238.10
Purchase #4	$139.57	12.677%	$157.2633	$157.26	$157.25	$157.30
Purchase #5	$162.91	9.810%	$178.8915	$178.89	$178.90	$178.90
Purchase #6	$153.39	9.225%	$167.5402	$167.54	$167.55	$167.50
Purchase #7	$153.89	3.155%	$158.7452	$158.75	$158.75	$158.70
7 purchase totals =	$1,233.02		$1,328.4839	$1,328.49	$1,328.50	$1,328.40