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	$217.77	11.410%	$242.6176	$242.62	$242.60	$242.60
Purchase #2	$37.78	4.846%	$39.6108	$39.61	$39.60	$39.60
Purchase #3	$13.75	4.244%	$14.3336	$14.33	$14.35	$14.30
Purchase #4	$7.50	4.294%	$7.8221	$7.82	$7.80	$7.80
Purchase #5	$99.90	3.376%	$103.2726	$103.27	$103.25	$103.30
Purchase #6	$35.37	4.566%	$36.985	$36.99	$37.00	$37.00
Purchase #7	$154.45	9.380%	$168.9374	$168.94	$168.95	$168.90
7 purchase totals =	$566.52		$613.5791	$613.58	$613.55	$613.50